2-methylthiopyrrolidines and their use for modulating bacterial quorum sensing

ABSTRACT

Compounds of Formula (I) are disclosed herein and their use in inhibiting quorum sensing in bacteria.

CROSS-REFERENCE TO RELATED APPLICATIONS

The benefit under 35 U.S.C. § 119(e) of U.S. Provisional PatentApplication No. 61/497,811, filed Jun. 16, 2011, is hereby claimed, thedisclosure of which is incorporated by reference in its entirety.

STATEMENT OF U.S. GOVERNMENT INTEREST

This invention was made with U.S. government support under CA 138176awarded by the National Institutes of Health. The government has acertain rights in the invention.

BACKGROUND

Quorum sensing (QS) is a type of bacterial cell-to-cell signalingpathway mediated through the production, release and detection of thesmall signaling molecules called autoinducers (AIs) (reviewed in (1)).Such communication allows bacterial control of crucial functions inunited communities for enhancement of symbiosis, virulence, antibioticproduction, biofilm formation, and many other processes. The recentincrease in prevalence of bacterial strains resistant to antibioticsemphasizes the need for the development of a new generation ofantibacterial agents. As QS is utilized by number of pathogenic bacteriato direct virulence and biofilm formation, inhibitors/modulators of QSmay serve as tools to study or intercept such community behaviors andmight be beneficial as antibacterial agents (2). One of the chemicalsignals, or autoinducers (AIs) used by Gram-negative bacteria are acylhomoserine lactones (AHLs), which are detected by their cognateregulator (R) proteins (1).

The QS system Vibrio fischeri (recently reclassified as Aliivibriofisheri) serves as the paradigm upon which all other QS systems arebased. It is composed of a transcriptional regulator protein (R) and asynthetase (I). The R protein is unstable unless it binds to the AHLwhich is produced by the synthetase. V. fischeri producesN-3-(oxo-hexanoyl)-homoserine lactone (3OC6HSL), V. harveyi synthesizesN-3-hydroxybutanoil-homoserine lactone (HAI-1), and Pseudomonasaeruginosa produces two distinct AHLs: N-3-oxo-dodecanoyl-L-homoserinelactone (3O-C12-HSL) and N-butyryl-L-homoserine lactone (C4-HSL). V.harveryi produces a second signalling molecule, a furnosyl boratediester, termed autoinducer-2 (AI-2), and a third CAI-1. CAI-1 has beenidentified in V. cholerae to be (s)-3 hydroxytridecan-4-one. P.aeruginosa also has a third QS signaling molecule,2-heptyl-3-hydroxy-4-quinolone (PQS), which is induced and repressed bythe las and rhl systems, respectively.

Pseudomonas aeruginosa is an important human opportunistic pathogenaffecting immunocompromised individuals, cancer patients, burn victims,cystic fibrosis patients and patients with impaired lung function. Ituses two AHL systems called, las and rhl to mediate QS. LasI/Rsynthesizes and detects N-(3-oxo-dodecanoyl)-L-homoserine lactone(3-oxo-C12-AHL) while RhlI/R synthesizes and detectsN-butanoyl-L-homoserine lactone (C4-AHL) (FIG. 1a ). In addition, P.aeruginosa has a third QS-dependent pathway, Pseudomonas quinolonesignal (PQS) that uses 2-heptyl-3-hydroxy-4-quinolone as an autoinducer(reviewed in (3)). Although, certain genes appear to be regulated by onepathway, for example regulation of genes involved in rhamnolipidsynthesis by the rhl pathway (4), there is much overlap between thepathways and what was once thought to be a hierarchical pathway, withlas activating rhl, is now known to be much more complex (5).Accumulated evidences clearly indicate the importance of P. aeruginosaQS in disease (6).

Over two decades, several small molecules have been identified by manyresearch groups as inhibitors of the AHL:R protein complex. These aremostly AHL-based structures with moderate changes on the acyl side chainand amide linkage. Some of the most potent inhibitors prepared by Geskeand Blackwell are shown in FIG. 1b (7). Recently, Meijler and co-workersdesigned a ligand, 3, which covalently modified LasR (8). Since AHL isthe pharamcophore present in the natural substrates, AHL-basedinhibitors are likely to modulate R protein activation.

Studies of structural features other than the AHL scaffold as tools tounderstand the R type protein interaction with AHLs are limited,although they might aid in rational design of QS inhibitors. Only a fewexamples of inhibitors with the altered lactone ring structure of AHLhave been reported (9-12). For example, Smith et al reported3-oxo-C12-(2-aminocyclohexanone) (FIG. 1 c, 4) as a strong antagonist ofLasR system (9), while Muh et al identified two LasR inhibitors having aphenyl and stetrazole ring (e.g. FIG. 1 c, 5), with IC50 in nM range(FIG. 1c ) (10). It is noteworthy that γ-thiolactone analogue of 1 (FIG.1b ) showed inhibition of LuxR while the corresponding ε-lactam(caprolactam) analogue was reported to lack LuxR binding (13). Thus, aneed exists for new QS inhibitors.

SUMMARY

Disclosed herein are compounds of formula (I):

wherein R¹ and R² are each independently H or OH, or R¹ and R² takentogether are oxo; R³ is C₂-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H,C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl or C₁-C₂₀alkylene-amino; R⁴ and R⁵ are eachindependently H or OH, or R⁴ and R⁵ taken together with the carbons thatthey are attached form a 4-7 membered cyclic or heterocyclic ring; X isNR⁶ or S; and R⁶ is H or C(O)alkyl; or a salt or ester thereof. Invarious embodiments, R¹ is OH and R² is H. In various cases, R¹ and R²together are oxo. In various cases, at least one of R⁴ and R⁵ is OH. Insome cases, both R⁴ and R⁵ are OH. In various cases, both R⁴ and R⁵ areH. In various cases, X is S. In various cases, X is NR⁶. In variouscases, R⁶ is H. In various cases, R⁶ is C(O)alkyl. In various cases, R³is C₃-C₁₂alkyl. In various cases, R³ is C₁-C₂₀alkyleneCO₂H. In variouscases, R³ is C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl. In various cases, R³ isC₁-C₂₀alkyleneCO₂-amino. In various cases, the compound of formula (I)has a structure selected from

Further provided herein are methods of inhibiting bacterial quorumsensing comprising contacting bacteria with a compound as disclosedherein, or a compound as disclosed herein formulated in a composition.In some cases, the bacteria are selected from Acinetobacter baumannii,Aeromonas hydrophila, Aeromonas salmonicida, Agrobacterium tumefaciens,Brucella melitensis, Burkholderia cenocepacia, Burkholderia mallei,Burkholderia pseudomallei, Burkholderia vietnamiensis, Chromobacteriumviolaceum, Enterobacter agglomeran, Erwinia carotovora, Erwiniachrysanthemi, Escherichia coli, Nitrosomas europaea, Obesumbacteriumproteus, Pantoea agglomerans, Pantoea stewartii, Pseudomonasaureofaciens, Pseudomonas aeruginosa, Pseudomonas fluorescens,Pseudomonas fuscovaginae, Pseudomonas syringae, Ralstonia solanacearum,Rhizobium etli, Rhizobium leguminosarum, Rhodobacter sphaeroides,Serratia liquefaciens, Serratia marcescens, Vibrio anguillarum, Vibriofischeri, Vibrio parahaemolyticus, Vibrio salmonicida, Xanthomonascampestris, Xenorhabdus nematophilus, Yersinia enterocolitica, Yersiniapestis, Yersinia pseudotuberculosis, Yersinia medievalis, Yersiniaruckeri, and combinations thereof. In various cases, the contactingcomprises administering to a subject suffering from a bacterialinfection. In some cases, the subject is human. In some cases, thesubject is an animal.

Further contemplated is administering a second agent to the subject,such as an antibiotic agent. Specific antibiotic agents contemplatedinclude a penicillin, a selexid, a cephalosporin, a tetracycline, arifamycin, gentamycin, clindamycin, a fluoroquinolone, a monobactamer, acarbapeneme, a macrolide, a polymyxin, an aminoglycoside, tobramycin, asulfonamide, a fusidine, a vancomycin, an oxazolidinone, ametronidazole, a corticosteroid, hydrocortisone, triamcinolone,betamethasone, and combinations thereof. The second agent and thecompound of formula (I) can be administered sequentially or at the sametime. In some cases, the second agent is administered before thecompound of formula (I), while in other cases, the second agent isadministered after the compound of formula (I). In some cases, thesecond agent and the compound of formula (I) are co-formulated.

Further provided herein are methods of treating a subject suffering froma bacterial infection comprising administering a compound as disclosedherein, or a compound as disclosed herein formulated in a composition.Also contemplated is further administering a second agent as disclosedherein, e.g., an antibiotic. In some cases, the infection is a P.aeruginosa infection.

Also provided herein are methods of inhibiting biofilm formationcomprising contacting bacteria with a compound as disclosed herein, or acompound as disclosed herein formulated in a composition.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows (a) AHL based signal molecules in P. aeruginosa. (b)Examples of most potent synthetic QS inhibitors in various Gram-negativebacteria along with their reported IC₅₀ values (7-8). (c) Examples of QSinhibitors with alteration of AHL scaffold (9-10).

FIG. 2 shows the effect of lactam and cyclic azahemiacetal derivativeson P_(lasI)-lacZ expression in E. coli tested at 50-200 μg/mLconcentrations against 2 μM of 3-oxo-C₁₂-AHL. P_(lasI)-lacZ activity isdepicted as percent activity relative to the DMSO treated control.Significance was determined by a paired two-tailed Student t-test and isdenoted as follows: *p-value<0.05, † p-value<0.02, ‡ p-value<0.01.

DETAILED DESCRIPTION

QS has been known to regulate a variety of cellular functions in manypathogenic bacteria including Pseudomonas aeruginosa. The QS machinery,including the two in P. aeruginosa, LasI/R and RhII/R, are based on theVibrio harveyi paradigm which includes a synthetase (I) and a regulatorprotein (R). The signaling molecule synthesized in Gram negativebacteria is acyl homoserine lactone (AHL) which activates QS. Inaddition, V. harveyi uses another signaling molecule, autoinducer II(AI-2), which is structurally different from AHLs, to activatebioluminescence. However, both bacteria use similar intermediates insynthesizing these signaling molecules, S-ribosylhomocysteine (SRH) andS-adenosyl-homocysteine (SAH) in V. harveyi and P. aeruginosa,respectively. Since it is known that QS deficient strains are lesspathogenic, alternative treatments that target the QS system are beingexplored.

To explore further effects of non-native AHL scaffold on QS, novellactam ligands were designed. Here, optically pure γ-lactams and cyclicazahemiacetals, bearing alkylthiometyl substituent with different lengthof carbon chain (C3-C12) are reported, which are capable of eitherinhibiting or, in some cases, inducing QS in P. aeruginosa. The lactamring was chosen because it is a more stable isoster of lactone ringpresent in AHL inhibitors. Moreover, the γ-lactam and cyclicazahemiacetal ligands were further modified in a such way that theyresemble S-ribosyl-L-homocysteine, which is known to regulate QS throughthe LuxS-mediated biosynthesis of AI-2 (1, 14-16), in which the riboseoxygen is replaced with a nitrogen atom and the homocysteine unit issubstituted with a simple alkylthiol chain. Described herein are analogsof SRH and SAH and their effect on V. harveyi and P. aeruginosa asdetermined by luminescence and a β-galactosidase assays. In particular,disclosed herein are compounds of formula (I):

wherein R¹ and R² are each independently H or OH, or R¹ and R² takentogether are oxo; R³ is C₂-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H, C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl or C₁-C₂₀alkylene-amino; R⁴ and R⁵ are eachindependently H or OH, or R⁴ and R⁵ taken together with the carbons thatthey are attached form a 4-7 membered cyclic or heterocyclic ring; X isNR⁶ or S; and R⁶ is H or C(O)alkyl; or a salt or ester thereof. In somecases, R¹ is OH and R² is H. In some cases, R¹ and R² taken together areoxo. In some cases, at least one of R⁴ and R⁵ is OH. In some cases, R⁴and R⁵ are each OH. In some cases, R⁴ and R⁵ are each H. In some cases,X is S. In some cases, X is NR⁶. In some cases, R⁶ is H. In some cases,R⁶ is C(O)alkyl. In some cases, R³ is C₃-C₁₂alkyl. In some cases. R³ isC₆-C₁₂alkyl. In some cases, R³ is C₁-C₂₀alkyleneCO₂H. In some cases, R³is C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl. In some cases, R³ isC₁-C₂₀alkyleneCO₂-amino.

The term “alkyl” used herein refers to a saturated or unsaturatedstraight or branched chain hydrocarbon group, including, but not limitedto, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,n-hexyl, and the like. Alkyls of one to six carbon atoms, three totwenty, three to twelve, four to twenty, four to twelve, five to twenty,five to twelve, six to twenty, six to twelve, seven to twenty, seven totwelve, eight to twenty, eight to twelve, nine to twenty, nine totwelve, and ten to twenty are also contemplated. The term “alkyl”includes “bridged alkyl,” i.e., a bicyclic or polycyclic hydrocarbongroup, for example, norbornyl, adamantyl, bicyclo[2.2.2]octyl,bicyclo[2.2.1]heptyl, bicyclo[3.2.1]octyl, or decahydronaphthyl. Alkylgroups optionally can be substituted, for example, with hydroxy (OH),halide, thiol (SH), aryl, heteroaryl, cycloalkyl, heterocycloalkyl, andamino.

As used herein, the term “cycloalkyl” refers to a cyclic hydrocarbongroup, e.g., cyclopropyl, cyclobutyl, cyclohexyl, and cyclopentyl.“Heterocycloalkyl” is defined similarly as cycloalkyl, except the ringcontains one to three heteroatoms independently selected from the groupconsisting of oxygen, nitrogen, and sulfur. Nonlimiting examples ofheterocycloalkyl groups include piperdine, tetrahydrofuran,tetrahydropyran, dihydrofuran, morpholine, thiophene, and the like.Cycloalkyl and heterocycloalkyl groups can be saturated or partiallyunsaturated ring systems optionally substituted with, for example, oneto three groups, independently selected from the group consisting ofalkyl, alkyleneOH, C(O)NH₂, NH₂, oxo (═O), aryl, haloalkyl, halo, andOH. Heterocycloalkyl groups optionally can be further N-substituted withalkyl, hydroxyalkyl, alkylenearyl, or alkyleneheteroaryl.

As used herein, the term “aryl” refers to a monocyclic or polycyclicaromatic group, preferably a monocyclic or bicyclic aromatic group,e.g., phenyl or naphthyl. Unless otherwise indicated, an aryl group canbe unsubstituted or substituted with one or more, and in particular oneto four groups independently selected from, for example, halo, alkyl,alkenyl, OCF₃, NO₂, CN, NC, OH, alkoxy, amino, CO₂H, CO₂alkyl, aryl, andheteroaryl. Exemplary aryl groups include, but are not limited to,phenyl, naphthyl, tetrahydronaphthyl, chlorophenyl, methylphenyl,methoxyphenyl, trifluoromethylphenyl, nitrophenyl,2,4-methoxychlorophenyl, and the like.

As used herein, the term “heteroaryl” refers to a monocyclic or bicyclicring system containing one or two aromatic rings and containing at leastone nitrogen, oxygen, or sulfur atom in an aromatic ring. Unlessotherwise indicated, a heteroaryl group can be unsubstituted orsubstituted with one or more, and in particular one to four,substituents selected from, for example, halo, alkyl, alkenyl, OCF₃,NO₂, CN, NC, OH, alkoxy, amino, CO₂H, CO₂alkyl, aryl, and heteroaryl. Insome cases, the heteroaryl group is substituted with one or more ofalkyl and alkoxy groups. Examples of heteroaryl groups include, but arenot limited to, thienyl, furyl, pyridyl, oxazolyl, quinolyl, thiophenyl,isoquinolyl, indolyl, triazinyl, triazolyl, isothiazolyl, isoxazolyl,imidazolyl, benzothiazolyl, pyrazinyl, pyrimidinyl, thiazolyl, andthiadiazolyl.

As used herein the term “amino” refers to a —NR₂ group, where each R isindependently hydrogen or alkyl, e.g., —NH₂, —NH(alkyl), or —N(alkyl)₂.When the amino is substituted with two alkyl groups, the alkyl groupscan be the same (e.g., —NMe₂) or different (e.g., —N(Me)(iPr)).

Of the analogs tested, four demonstrated anti-QS activity(S-[2-Oxopyrrolidin-5-yl)methyl)]thiopropanol[5-(Propylthiomethyl)pyrrolidin-2-one] (OMPP),S-[2-Oxopyrrolidin-5-yl)methyl)]thiopropanol[5-Hexylthiomethyl)pyrrolidin-2-one] (OMHP),S-[N-Benzyl-3,4-dihyroxy-2-oxopyrrolidin-5-yl)methyl]-L-homocysteine(BDOH), andS-[2-Hydroxypyrrolidin-5-yl)methyl]thiopropanol[5-Propylthiomethyl)-2-hydroxy-pyrrolidin](HMPP)). BDOH and HMPP exhibited a strong anti-QS effect against V.harveyi. OMPP and OMHP had a dosed dependent inhibition on theexpression of the lasI promoter of P. aeruginosa. The data presentedherein demonstrates that the analogs described herein can be used tointerrupt bacterial communication in difference bacteria and would beuseful as an effective treatment for bacterial infections.

Compounds disclosed herein show selectivity between two QS systems,acting as inhibitors against las signaling and moderate activatorsagainst rhl signaling, possibly due to differences in the active sitesof their cognate R proteins or transport of the native signalingmolecule. Anatognism of las activity increased with the length of thealkylthio chain. Interestingly, the cyclic azahemiacetal derivativeswith shorter alkylthio chain were found to stimulate both QS systems atlower concentrations while strongly inhibiting at higher concentrations.The ribolactam and the corresponding cyclic azahemiacetal analoguesinhibited las and stimulated rhl moderately. Although, the mechanism ofinhibition is still unknown, it is plausible that the compounds act ascompetitive inhibitors by binding to the QS sensor or affect eventsdownstream, such as the binding of lasR (or in some cases, rhlR) to thepromoter. Affecting downstream events would require that the compoundenter the cells, which is unknown. Alternatively, it is established thatalthough the rhl signaling molecule, C₄-AHL diffuses freely, transportof the las signaling molecule is more complex, involving partitioninginto the membrane and transport out of the cell by the MexAB-OprM effluxpump (27). Thus, it is also possible that the compounds with longer sidechains affect the membrane and that the las pathway is more sensitive tothese changes. Given the central role the las and rhl QS pathways playin P. aeruginosa virulence, inhibitors such as the ones described here,have significant potential as therapeutics.

Specific compounds of formula (I) contemplated include:

Asymmetric carbon atoms can be present. All such isomers, includingdiastereomers and enantiomers, as well as the mixtures thereof, areintended to be included in the scope of the disclosure herein. Incertain cases, compounds can exist in tautomeric forms. All tautomericforms are intended to be included in the scope of the disclosure herein.Likewise, when compounds contain an alkenyl or alkenylene group, thereexists the possibility of cis- and trans-isomeric forms of thecompounds. Both cis- and trans-isomers, as well as the mixtures of cis-and trans-isomers, are contemplated.

The salts, e.g., pharmaceutically acceptable salts, of the disclosedtherapeutics may be prepared by reacting the appropriate base or acidwith a stoichiometric equivalent of the therapeutic.

Acids commonly employed to form pharmaceutically acceptable saltsinclude inorganic acids such as hydrogen bisulfide, hydrochloric acid,hydrobromic acid, hydroiodic acid, sulfuric acid and phosphoric acid, aswell as organic acids such as para-toluenesulfonic acid, salicylic acid,tartaric acid, bitartaric acid, ascorbic acid, maleic acid, besylicacid, fumaric acid, gluconic acid, glucuronic acid, formic acid,glutamic acid, methanesulfonic acid, ethanesulfonic acid,benzenesulfonic acid, lactic acid, oxalic acid, para-bromophenylsulfonicacid, carbonic acid, succinic acid, citric acid, benzoic acid and aceticacid, as well as related inorganic and organic acids. Suchpharmaceutically acceptable salts thus include sulfate, pyrosulfate,bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate,dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide,iodide, acetate, propionate, decanoate, caprylate, acrylate, formate,isobutyrate, caprate, heptanoate, propiolate, oxalate, malonate,succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate,hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate,dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate,terephthalate, sulfonate, xylene sulfonate, phenylacetate,phenylpropionate, phenylbutyrate, citrate, lactate, O-hydroxybutyrate,glycolate, maleate, tartrate, methanesulfonate, propanesulfonate,naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and othersalts. In one embodiment, pharmaceutically acceptable acid additionsalts include those formed with mineral acids such as hydrochloric acidand hydrobromic acid, and especially those formed with organic acidssuch as maleic acid.

Pharmaceutically acceptable base addition salts may be formed withmetals or amines, such as alkali and alkaline earth metals or organicamines. Pharmaceutically acceptable salts of compounds may also beprepared with a pharmaceutically acceptable cation. Suitablepharmaceutically acceptable cations are well known to those skilled inthe art and include alkaline, alkaline earth, ammonium and quaternaryammonium cations. Carbonates or hydrogen carbonates are also possible.Examples of metals used as cations are sodium, potassium, magnesium,ammonium, calcium, or ferric, and the like. Examples of suitable aminesinclude isopropylamine, trimethylamine, histidine,N,N′-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine,dicyclohexylamine, ethylenediamine, N-methylglucamine, and procaine.

Similarly, pharmaceutically acceptable derivatives (e.g., esters),metabolites, hydrates, solvates and prodrugs of the therapeutic may beprepared by methods generally known to those skilled in the art. Thus,another embodiment provides compounds that are prodrugs of an activecompound. In general, a prodrug is a compound which is metabolized invivo (e.g., by a metabolic transformation such as deamination,dealkylation, de-esterification, and the like) to provide an activecompound. A “pharmaceutically acceptable prodrug” means a compound whichis, within the scope of sound medical judgment, suitable forpharmaceutical use in a patient without undue toxicity, irritation,allergic response, and the like, and effective for the intended use,including a pharmaceutically acceptable ester as well as a zwitterionicform, where possible, of the therapeutic. As used herein, the term“pharmaceutically acceptable ester” refers to esters that hydrolyze invivo and include those that break down readily in the human body toleave the parent compound or a salt thereof. Suitable ester groupsinclude, for example, those derived from pharmaceutically acceptablealiphatic carboxylic acids, particularly alkanoic, alkenoic,cycloalkanoic and alkanedioic acids, in which each alkyl or alkenylmoiety advantageously has not more than 6 carbon atoms. Representativeexamples of particular esters include, but are not limited to, formates,acetates, propionates, butyrates, acrylates and ethylsuccinates.Examples of pharmaceutically-acceptable prodrug types are described inHiguchi and Stella, Pro-drugs as Novel Delivery Systems, Vol. 14 of theA.C.S. Symposium Series, and in Roche, ed., Bioreversible Carriers inDrug Design, American Pharmaceutical Association and Pergamon Press,1987, both of which are incorporated herein by reference.

The compounds and compositions described herein may also includemetabolites. As used herein, the term “metabolite” means a product ofmetabolism of a compound of the embodiments or a pharmaceuticallyacceptable salt, analog, or derivative thereof, that exhibits a similaractivity in vitro or in vivo to a disclosed therapeutic. The compoundsand compositions described herein may also include hydrates andsolvates. As used herein, the term “solvate” refers to a complex formedby a solute (herein, the therapeutic) and a solvent. Such solvents forthe purpose of the embodiments preferably should not negativelyinterfere with the biological activity of the solute. Solvents may be,by way of example, water, ethanol, or acetic acid.

Pharmaceutical Compositions

The terms “therapeutically effective amount” and “prophylacticallyeffective amount,” as used herein, refer to an amount of a compoundsufficient to treat, ameliorate, or prevent the identified disease orcondition, or to exhibit a detectable therapeutic, prophylactic, orinhibitory effect. The effect can be detected by, for example, animprovement in clinical condition, reduction in symptoms, or by any ofthe assays or clinical diagnostic tests described herein. The preciseeffective amount for a subject will depend upon the subject's bodyweight, size, and health; the nature and extent of the condition; andthe therapeutic or combination of therapeutics selected foradministration. Therapeutically and prophylactically effective amountsfor a given situation can be determined by routine experimentation thatis within the skill and judgment of the clinician.

Dosages of the therapeutic can alternately be administered as a dosemeasured in mg/kg. Contemplated mg/kg doses of the disclosedtherapeutics include about 0.001 mg/kg to about 1000 mg/kg. Specificranges of doses in mg/kg include about 0.1 mg/kg to about 500 mg/kg,about 0.5 mg/kg to about 200 mg/kg, about 1 mg/kg to about 100 mg/kg,about 2 mg/kg to about 50 mg/kg, and about 5 mg/kg to about 30 mg/kg.

As herein, the compounds described herein may be formulated inpharmaceutical compositions with a pharmaceutically acceptableexcipient, carrier, or diluent. The compound or composition comprisingthe compound is administered by any route that permits treatment of thedisease or condition. One route of administration is oraladministration. Additionally, the compound or composition comprising thecompound may be delivered to a patient using any standard route ofadministration, including parenterally, such as intravenously,intraperitoneally, intrapulmonary, subcutaneously or intramuscularly,intrathecally, topically, transdermally, rectally, orally, nasally or byinhalation. Slow release formulations may also be prepared from theagents described herein in order to achieve a controlled release of theactive agent in contact with the body fluids in the gastro intestinaltract, and to provide a substantial constant and effective level of theactive agent in the blood plasma. The crystal form may be embedded forthis purpose in a polymer matrix of a biological degradable polymer, awater-soluble polymer or a mixture of both, and optionally suitablesurfactants. Embedding can mean in this context the incorporation ofmicro-particles in a matrix of polymers. Controlled release formulationsare also obtained through encapsulation of dispersed micro-particles oremulsified micro-droplets via known dispersion or emulsion coatingtechnologies.

Administration may take the form of single dose administration, or acompound as disclosed herein can be administered over a period of time,either in divided doses or in a continuous-release formulation oradministration method (e.g., a pump). However the compounds of theembodiments are administered to the subject, the amounts of compoundadministered and the route of administration chosen should be selectedto permit efficacious treatment of the disease condition.

In an embodiment, the pharmaceutical compositions are formulated withone or more pharmaceutically acceptable excipient, such as carriers,solvents, stabilizers, adjuvants, diluents, etc., depending upon theparticular mode of administration and dosage form. The pharmaceuticalcompositions should generally be formulated to achieve a physiologicallycompatible pH, and may range from a pH of about 3 to a pH of about 11,preferably about pH 3 to about pH 7, depending on the formulation androute of administration. In alternative embodiments, the pH is adjustedto a range from about pH 5.0 to about pH 8. More particularly, thepharmaceutical compositions may comprise a therapeutically orprophylactically effective amount of at least one compound as describedherein, together with one or more pharmaceutically acceptableexcipients. Optionally, the pharmaceutical compositions may comprise acombination of the compounds described herein, or may include a secondactive ingredient useful in the treatment or prevention of bacterialinfection (e.g., anti-bacterial or anti-microbial agents.

Formulations, e.g., for parenteral or oral administration, are mosttypically solids, liquid solutions, emulsions or suspensions, whileinhalable formulations for pulmonary administration are generallyliquids or powders. A pharmaceutical composition can also be formulatedas a lyophilized solid that is reconstituted with a physiologicallycompatible solvent prior to administration. Alternative pharmaceuticalcompositions may be formulated as syrups, creams, ointments, tablets,and the like.

The term “pharmaceutically acceptable excipient” refers to an excipientfor administration of a pharmaceutical agent, such as the compoundsdescribed herein. The term refers to any pharmaceutical excipient thatmay be administered without undue toxicity.

Pharmaceutically acceptable excipients are determined in part by theparticular composition being administered, as well as by the particularmethod used to administer the composition. Accordingly, there exists awide variety of suitable formulations of pharmaceutical compositions(see, e.g., Remington's Pharmaceutical Sciences).

Suitable excipients may be carrier molecules that include large, slowlymetabolized macromolecules such as proteins, polysaccharides, polylacticacids, polyglycolic acids, polymeric amino acids, amino acid copolymers,and inactive virus particles. Other exemplary excipients includeantioxidants (e.g., ascorbic acid), chelating agents (e.g., EDTA),carbohydrates (e.g., dextrin, hydroxyalkylcellulose, and/orhydroxyalkylmethylcellulose), stearic acid, liquids (e.g., oils, water,saline, glycerol and/or ethanol) wetting or emulsifying agents, pHbuffering substances, and the like. Liposomes are also included withinthe definition of pharmaceutically acceptable excipients.

The pharmaceutical compositions described herein are formulated in anyform suitable for an intended method of administration. When intendedfor oral use for example, tablets, troches, lozenges, aqueous or oilsuspensions, non-aqueous solutions, dispersible powders or granules(including micronized particles or nanoparticles), emulsions, hard orsoft capsules, syrups or elixirs may be prepared. Compositions intendedfor oral use may be prepared according to any method known to the artfor the manufacture of pharmaceutical compositions, and suchcompositions may contain one or more agents including sweetening agents,flavoring agents, coloring agents and preserving agents, in order toprovide a palatable preparation.

Pharmaceutically acceptable excipients particularly suitable for use inconjunction with tablets include, for example, inert diluents, such ascelluloses, calcium or sodium carbonate, lactose, calcium or sodiumphosphate; disintegrating agents, such as cross-linked povidone, maizestarch, or alginic acid; binding agents, such as povidone, starch,gelatin or acacia; and lubricating agents, such as magnesium stearate,stearic acid or talc.

Tablets may be uncoated or may be coated by known techniques includingmicroencapsulation to delay disintegration and adsorption in thegastrointestinal tract and thereby provide a sustained action over alonger period. For example, a time delay material such as glycerylmonostearate or glyceryl distearate alone or with a wax may be employed.

Formulations for oral use may be also presented as hard gelatin capsuleswherein the active ingredient is mixed with an inert solid diluent, forexample celluloses, lactose, calcium phosphate or kaolin, or as softgelatin capsules wherein the active ingredient is mixed with non-aqueousor oil medium, such as glycerin, propylene glycol, polyethylene glycol,peanut oil, liquid paraffin or olive oil.

In another embodiment, pharmaceutical compositions may be formulated assuspensions comprising a compound of the embodiments in admixture withat least one pharmaceutically acceptable excipient suitable for themanufacture of a suspension.

In yet another embodiment, pharmaceutical compositions may be formulatedas dispersible powders and granules suitable for preparation of asuspension by the addition of suitable excipients.

Excipients suitable for use in connection with suspensions includesuspending agents (e.g., sodium carboxymethylcellulose, methylcellulose,hydroxypropyl methylcellulose, sodium alginate, polyvinylpyrrolidone,gum tragacanth, gum acacia); dispersing or wetting agents (e.g., anaturally occurring phosphatide (e.g., lecithin), a condensation productof an alkylene oxide with a fatty acid (e.g., polyoxyethylene stearate),a condensation product of ethylene oxide with a long chain aliphaticalcohol (e.g., heptadecaethyleneoxycethanol), a condensation product ofethylene oxide with a partial ester derived from a fatty acid and ahexitol anhydride (e.g., polyoxyethylene sorbitan monooleate)); andthickening agents (e.g., carbomer, beeswax, hard paraffin or cetylalcohol). The suspensions may also contain one or more preservatives(e.g., acetic acid, methyl or n-propyl p-hydroxy-benzoate); one or morecoloring agents; one or more flavoring agents; and one or moresweetening agents such as sucrose or saccharin.

The pharmaceutical compositions may also be in the form of oil-in wateremulsions. The oily phase may be a vegetable oil, such as olive oil orarachis oil, a mineral oil, such as liquid paraffin, or a mixture ofthese. Suitable emulsifying agents include naturally-occurring gums,such as gum acacia and gum tragacanth; naturally occurring phosphatides,such as soybean lecithin, esters or partial esters derived from fattyacids; hexitol anhydrides, such as sorbitan monooleate; and condensationproducts of these partial esters with ethylene oxide, such aspolyoxyethylene sorbitan monooleate. The emulsion may also containsweetening and flavoring agents. Syrups and elixirs may be formulatedwith sweetening agents, such as glycerol, sorbitol or sucrose. Suchformulations may also contain a demulcent, a preservative, a flavoringor a coloring agent.

Additionally, the pharmaceutical compositions may be in the form of asterile injectable preparation, such as a sterile injectable aqueousemulsion or oleaginous suspension. This emulsion or suspension may beformulated by a person of ordinary skill in the art using those suitabledispersing or wetting agents and suspending agents, including thosementioned above. The sterile injectable preparation may also be asterile injectable solution or suspension in a non-toxic parenterallyacceptable diluent or solvent, such as a solution in 1,2-propane-diol.

The sterile injectable preparation may also be prepared as a lyophilizedpowder. Among the acceptable vehicles and solvents that may be employedare water, Ringer's solution, and isotonic sodium chloride solution. Inaddition, sterile fixed oils may be employed as a solvent or suspendingmedium. For this purpose any bland fixed oil may be employed includingsynthetic mono- or diglycerides. In addition, fatty acids (e.g., oleicacid) may likewise be used in the preparation of injectables.

To obtain a stable water-soluble dose form of a pharmaceuticalcomposition, a pharmaceutically acceptable salt of a compound describedherein may be dissolved in an aqueous solution of an organic orinorganic acid, such as 0.3 M solution of succinic acid, or morepreferably, citric acid. If a soluble salt form is not available, thecompound may be dissolved in a suitable co-solvent or combination ofco-solvents. Examples of suitable co-solvents include alcohol, propyleneglycol, polyethylene glycol 300, polysorbate 80, glycerin and the likein concentrations ranging from about 0 to about 60% of the total volume.In one embodiment, the active compound is dissolved in DMSO and dilutedwith water.

The pharmaceutical composition may also be in the form of a solution ofa salt form of the active ingredient in an appropriate aqueous vehicle,such as water or isotonic saline or dextrose solution. Also contemplatedare compounds which have been modified by substitutions or additions ofchemical or biochemical moieties which make them more suitable fordelivery (e.g., increase solubility, bioactivity, palatability, decreaseadverse reactions, etc.), for example by esterification, glycosylation,PEGylation, etc.

In some embodiments, the compounds described herein may be formulatedfor oral administration in a lipid-based formulation suitable for lowsolubility compounds. Lipid-based formulations can generally enhance theoral bioavailability of such compounds.

As such, pharmaceutical compositions comprise a therapeutically orprophylactically effective amount of a compound described herein,together with at least one pharmaceutically acceptable excipientselected from the group consisting of medium chain fatty acids andpropylene glycol esters thereof (e.g., propylene glycol esters of ediblefatty acids, such as caprylic and capric fatty acids) andpharmaceutically acceptable surfactants, such as polyoxyl 40hydrogenated castor oil.

In some embodiments, cyclodextrins may be added as aqueous solubilityenhancers. Exemplary cyclodextrins include hydroxypropyl, hydroxyethyl,glucosyl, maltosyl and maltotriosyl derivatives of α-, β-, andβ-cyclodextrin. A specific cyclodextrin solubility enhancer ishydroxypropyl-o-cyclodextrin (BPBC), which may be added to any of theabove-described compositions to further improve the aqueous solubilitycharacteristics of the compounds of the embodiments. In one embodiment,the composition comprises about 0.1% to about 20%hydroxypropyl-o-cyclodextrin, more preferably about 1% to about 15%hydroxypropyl-o-cyclodextrin, and even more preferably from about 2.5%to about 10% hydroxypropyl-o-cyclodextrin. The amount of solubilityenhancer employed will depend on the amount of the compound of theinvention in the composition.

Quorum Sensing

Some bacteria have a system by which they can monitor the density oftheir own population and control the expression of specific genes onlywhen a certain population density has been reached. This ability tomonitor cell density has been found in more than 20 different bacterialspecies, and has been termed quorum sensing. Pathogenic bacteria usequorum sensing to turn on virulence pathways and form drug-imperviouscommunities called biofilms that are the basis of a myriad chronicinfections. Over 80% of bacterial infections in humans involve theformation of biofilms, as exemplified in lung infections by Pseudomonasaeruginosa, which is the primary cause of morbidity in cystic fibrosispatients.

The existence of quorum sensing was established in the early 1970s whereexperiments showed that bioluminescence of the bacterium Vibrio fischeriis a function of cell density, and that it is controlled by a smalldiffusible molecule, later identified to be a N-acyl-homoserine lactone(AHL), namely N-(3-oxohexanoyl)-L-homoserine lactone.

The quorum sensing system of V. fischeri serves well as a basis fordescribing and understanding quorum sensing systems. It comprises asignal molecule synthase (LuxI) which produces the signal molecule (AHL,in casu N-(oxo-hexanoyl)-L-homoserine lactone) from a precursor, and asignal molecule dependent receptor protein (LuxR). When theconcentration of the signal molecule reaches a threshold level, i.e.when the population of the bacterium reaches a certain level, the signalmolecule interacts with the receptor protein to effect an activation ofit. The LuxR-AHL complex binds to the lux box in the promoter region ofthe gene, which, in turn, initiates the transcription of luxI (the geneencoding LuxI) and other genes responsible for bioluminescense. The LuxIproduction thus generates a positive autoregulatory loop. The signalmolecules are often referred to as autoinducers.

Many Gram-negative bacteria have been shown to posses one or more quorumsensing systems homologues to the LuxR/LuxI system just described for V.fischeri, and Pseudomonas aeruginosa in particular appears to have atleast two quorum sensing systems, i.e. las and rhl. The las systemcomprises a signal molecule generating synthase (LasI), the majorproduct of which is N-(3-oxo-dodecanoyl)-homoserine lactone (OdDHL), anda receptor protein LasR. The rhl system comprises a signal generatingsynthase (RhlI), the major product of which is N-butyryl-homoserinelactone, and a receptor protein RhlR. The las system modulates theexpression of LasI, RhlI, LasR and virulence factors, such as elastase,staphylolytic protease, alkaline protease, exotoxin and neuraminidase,and biofilm differentiation. The rhl system modulates the expression ofRhlI, rhamnolipid and virulence factors, such as alkaline protease,elastase, haemolysin, pyocyanin and hydrogen cyanide. Moreover, in vitroimmunoassays on human leukocytes have shown that OdDHL possessesimmunomodulatory properties, e.g. inhibition of lymphocyte proliferationand down-regulation of tumor necrosis factor alpha production and ofIL-12 production (Telford et al., Infect. Immun, 66, 36, 1998). Inaddition, OdDHL has been demonstrated to activate T-cells in vivo toproduce the inflammatory cytokine interferon-γ (Smith et al., J.Immunol., 167, 366, 2001) and, thereby, potentially promote aTh2-dominated response leading to increased tissue damage andinflammation.

An important effect of a quorum sensing system is that, e.g. virulencefactors are only excreted when the population has reached a certaindensity. This is probably of vital importance for invading organismsbecause they, at low density, are more susceptible to the defensesystems of the host. If an invading organism unveiled its presence byexcreting virulence factors when still at a low population density, theywould be more easily targeted by the host's defense mechanisms A quorumsensing system endows bacteria with a capability to reach a criticalpopulation density whereby they overwhelm the host's immune defense andestablish an infection.

The rationale behind quorum sensing based drugs is multifaceted. Bypreventing the excretion of virulence factors, the pathogenecity of theinvading organism is diminished, or even eliminated. Furthermore, asdescribed above, the signal molecules may themselves have an adverseeffect on the immune system of the host, so inhibiting the production ofsignal molecules will have a beneficial effect. Finally, the developmentof persistent biofilms in some bacteria, e.g. Pseudomonas aeruginosa isalso affected by the quorum sensing system (Hentzer et al., Microbiology148, 87, 2002). Although the biofilm itself may not be virulent, itprotects the invading organism from the defense systems of the host. Bypreventing the formation of persistent biofilms, the invading organismis left exposed to the defense systems of the host, and the host maythus be able to clear the infection on its own. Alternatively, theinfectious organism will be left more receptive to treatment withconventional antibiotics. It is thus envisaged that an embodiment of theinvention involving a combination treatment, wherein a quorum sensinginhibitor of the present invention and an antibiotic is administered toa patient will be particular beneficial for certain types of infections.

Inhibiting the quorum sensing system as such will not have a toxiceffect on the bacterium, and, while not wishing to be bound by theory,it is believed that this will have an impact on the build-up ofresistance towards such drugs. Resistance to antibiotics is generatedunder the imposition of a selection pressure favoring mutants that arecapable of tolerating the toxins. Quorum sensing inhibitors as such canbe non-toxic, and they are therefore not expected to impose a selectionpressure on the bacteria. As a consequence, the formation of resistantstrains is expected to be at a minimum, i.e. the background mutationalrate. Toxicity may be quantified in a simple assay wherein the bacteriumEscherichia coli is left to grow planktonic in the absence or presenceof a test compound. Bacterial cultures are grown in ABt minimal mediumsupplemented with 0.5% casamino acids and 0.5% glucose (referred to asgrowth medium). The ABt medium contains: (NH)₂SO₄ (2 g/L), Na₂HPO₄.2H₂O(6 g/L), KH₂PO₄ (3 g/L), NaCl (3 g/L), MgCl₂ (93 mg/L), CaCl₂ (11 mg/l),and thiamine (0.5 mg/L). Culture conditions: The 20 ml cultures weregrown in 100 ml conical flasks in an orbital air shaker at 200 rpm at37° C. The cultures are inoculated from overnight cultures in freshmedium at an optical density of approximately OD₄₅₀=0.2. The culturesare grown to OD₄₅₀=1.0, then diluted in fresh test medium to OD₄₅₀=0.2.Growth is monitored by OD₄₅₀ every 5 min. Compounds, which atconcentration lower than 10 mM, lower than 1 mM, lower than 500 μM, orlower than 100 μM cause an increase of the doubling time during theexponential growth phase relative to the doubling time in the absence ofthe compound by more than 5%, e.g. 10%, e.g. more than 30%, such as morethan 60%, such as more than 95% are said to be toxic.

The absence of toxicity is also believed to reduce the number of adverseeffects. Treatments involving traditional antibiotics are oftenconnected with unpleasant side effect, e.g. diarrhea caused by theeffect of the antibiotics on the beneficial bacteria present in the gut.As quorum sensing inhibitors are non-toxic, they are not expected toaffect other bacteria than those exploiting a quorum sensing system andthe number of adverse effects is thus likely to be reduced.

Different assays are described in the literature by which to assess if agiven compound is a quorum sensing inhibitor. WO 00/06177 discloses amethod that assesses the extent to which the activity of the signalmolecule synthase is modulated by a given test compound. The methodprovides a labeled homoserine lactone substrate, allows the reaction toproceed to completion and determines the extent of the homoserinelactone substrate to homoserine lactone conversion in the absence andpresence of the test compound. Wu, et al., Microbiol 146, 2481, 2000,and Andersen et al., Appl. Envirom. Microbiol., 67, 575, 2001, describehow part of the quorum sensing system, i.e. the luxR and the luxIpromoter from Vibrio fischeri may be fused with a gene encoding unstableversions (Andersen et al., Appl Environ Microbiol 64, 2240, 1998) of thegreen fluorescence protein (GFP). This fusion (referred to as theLuxR-QS-monitor) may be incorporated into bacterial strains which, ifexposed to a signal molecule, will produce GFP which can be detected byepifluorescence spectroscopy. WO 01/18248 discloses the use of otherreporter genes than GFP, e.g. luciferase. The quorum sensing inhibitingeffect of a given compound may also be quantified in an assay whereinthe lasR and the lasB promoter from Pseudomonas aeruginosa fused withthe gene encoding unstable GFP (referred to as the LasR-QS-monitor) isincorporated into the chromosome of Pseudomonas aeruginosa or a plasmidvehicle as disclosed in Hentzer et al, Microbiol, 148, 87, 2002.

Manefield et al, Microbiology, 148, 1119, 2002, describe a method toscientifically demonstrate and quantify the QSI activity of compounds.E. coli, into which the LuxR-QS-monitor was incorporated, was inoculatedfrom an overnight culture in fresh culture medium at a density ofapproximately OD₄₅₀=1, and incubated at 37° C. for approximately 30 min.Aliquots (200 μl) of this culture were distributed to the wells ofmicrotiter dishes into which a known signal molecule, namelyΛ/-(3-oxo-hexanoyl)-L-homoserine lactone (OHHL) at 25, 50 and 100 nM,and the test compound had been pipetted. After two hours of incubationat 37° C. the relative fluorescence units (RFU) of each sample werecaptured with in Wallac Victor2, 1420 Multilabel Counter using a 485 nmexcitation filter and a 535 nm emission filter. The RFU values obtainedfor each concentration were used to calculate an inhibition indexexpressing the quantity of test compound per quantity of OHHL requiredto inhibit LuxR controlled P_(luxI)-GFP expression to a given level (X%). This is termed the IDX value. The three values obtained, one foreach OHHL concentration, were plotted as a function of OHHLconcentration and the gradient of the best straight line fitted to thethree points and passing through the origin was taken as the inhibitionindex (IIX). The IIX expresses the number of μmol of test compound pernanomole OHHL required to inhibit expression of fluorescence to X % ofthe untreated sample. A low IIX value may therefore be interpreted as toreflect a compound with high efficacy. Test compounds with IIX lowerthan 10, lower than 5, lower than 1, lower than 0.5, lower than 0.1, orlower than 0.05 for X higher than 10%, such as higher than 20%, higherthan 40%, higher than 60%, higher than 95% exhibit quorum sensinginhibition.

The assays discussed above use parts of the quorum sensing system fromparticular bacteria incorporated into particular bacteria. Despite that,it has been found that such reporter systems function in a number ofdifferent bacteria, and that they are responsive to a variety of quorumsensing inhibitors (Manefield et al, Microbiology, 148, 1119, 2002). Theapplied assay is therefore useful to identify compounds which inhibitthe quorum sensing system in a wide range of bacteria, e.g. Pseudomonasaeruginosa.

Gram-negative bacteria represent numerous relevant pathogens usingquorum-sensing pathways. Besides P. aeruginosa, other Gram-negativequorum sensing bacteria include: Acinetobacter baumannii, Aeromonashydrophila, Aeromonas salmonicida, Agrobacterium tumefaciens, Brucellamelitensis, Burkholderia cenocepacia, Burkholderia mallei, Burkholderiapseudomallei, Burkholderia vietnamiensis, Chromobacterium violaceum,Enterobacter agglomeran, Erwinia carotovora, Erwinia chrysanthemi,Escherichia coli, Nitrosomas europaea, Obesumbacterium proteus, Pantoeaagglomerans, Pantoea stewartii, Pseudomonas aureofaciens, Pseudomonasfluorescens, Pseudomonas fuscovaginae, Pseudomonas syringae, Ralstoniasolanacearum, Rhizobium etli, Rhizobium leguminosarum, Rhodobactersphaeroides Rhodobacter sphaeroides, Serratia liquefaciens, Serratiamarcescens, Vibrio anguillarum, Vibrio cholerae, Vibrio fisheri, Vibrioparahaemolyticus, Vibrio salmonicida, Xenorhabdus nematophilus, Yersiniaenterocolitica, Yersinia pestis, Yersinia pseudotuberculosis, Yersiniamedievalis, and Yersinia ruckeri.

Methods of Treatment

Biofilms are dense extracellular polymeric matrices in which bacteriaembed themselves. Biofilms allow bacteria to create a microenvironmentthat attaches the bacteria to the host surface and which containsexcreted enzymes and other factors allowing the bacteria to evade hostimmune responses including antibodies and cellular immune responses.Such biofilms can also exclude antibiotics. Further, biofilms can beextremely resistant to removal and disinfection. For individualssuffering from cystic fibrosis, the formation of biofilms by P.aeruginosa is eventually fatal. Other bacteria also respond to quorumsensing signals by producing biofilms. Biofilms are inherent in dentalplaques, and are found on surgical instruments, food processing andagriculture equipment and water treatment and power generating machineryand equipment.

Thus, provided herein is a method of treating a disorder associated withquorum sensing or biofilm formation in a mammalian subject, the methodcomprising administering a compound of formula (I) as disclosed hereinto the subject in an amount effective to disrupt quorum sensing orbiofilm formation in the subject. The subject can be human, animal, orplant. In some specific cases, the subject is human. In some specificcases, the subject is an animal. Specifically contemplated animalsubjects include fish and amphibians. In some specific cases, thesubject is a plant.

In various embodiments, the disorder associated with biofilm formationin the subject is selected from the group consisting of cystic fibrosis,dental caries, periodonitis, otitis media, muscular skeletal infections,necrotizing fasciitis, biliary tract infection, osteomyelitis, bacterialprostatitis, endocarditis, native valve endocarditis, cystic fibrosispneumonia, meloidosis, or skin lesions associated with bullous impetigo,atopic dermatitis and pemphigus foliaceus or implanted device-relatedinfections. In some embodiments, the condition is a nosocomialinfection, including but not limited to, pneumonia or an infectionassociated with sutures, exit sites, arteriovenous sites, scleralbuckles, contact lenses, urinary catheter cystitis, peritoneal dialysis(CAPD) peritonitis, IUDs, endotracheal tubes, Hickman catheters, centralvenous catheters, mechanical heart valves, vascular grafts, biliarystent blockage, and orthopedic devices.

Also provided is a method of modulating biofilm formation on a surface,the method comprising contacting the surface with a compound of formula(I) as disclosed herein in an amount effective for disrupt or inhibitbiofilm formation on the surface. In one embodiment, the surface is aninanimate surface. Exemplary inanimate surfaces include, but are notlimited to, metal, glass, plastic, wood and stone surfaces. In anotherembodiment, the surface is an animate surface. Exemplary animatesurfaces include, but are not limited to, mammalian tissues, mammalianmembranes, mammalian skin.

As used herein, the term “pathogenic bacterium” or “pathogenic bacteria”refers to both gram-negative and gram-positive bacterial cells capableof infecting and causing disease in a mammalian host, as well asproducing infection-related symptoms in the infected host, such as feveror other signs of inflammation, intestinal symptoms, respiratorysymptoms, dehydration, and the like.

In some embodiments, and without limitation, the bacteria is of a genusselected from the group consisting of Aeromonas, Agrobacterium,Burkholderia, Chromobacterium, Enterobacter, Erwinia, Escherichia,Nitrosomas, Obesumbacterium, Pantoea, Pseudomonas, Ralstonia, Rhisobium,Rhodobacter, Serratia, Staphylococcus, Vibrio, Xenorhabdus, andYersinia. For example, in some embodiments and without limitation, thebacteria is of a species selected from the group consisting of:Acinetobacter baumannii, Aeromonas hydrophila, Aeromonas salmonicida,Agrobacterium tumefaciens, Brucella melitensis, Burkholderiacenocepacia, Burkholderia mallei, Burkholderia pseudomallei,Burkholderia vietnamiensis, Chromobacterium violaceum, Enterobacteragglomeran, Erwinia carotovora, Erwinia chrysanthemi, Escherichia coli,Nitrosomas europaea, Obesumbacterium proteus, Pantoea agglomerans,Pantoea stewartii, Pseudomonas aureofaciens, Pseudomonas aeruginosa,Pseudomonas fluorescens, Pseudomonas fuscovaginae, Pseudomonas syringae,Ralstonia solanacearum, Rhizobium etli, Rhizobium leguminosarum,Rhodobacter sphaeroides, Serratia liquefaciens, Serratia marcescens,Vibrio anguillarum, Vibrio fischeri, Vibrio parahaemolyticus, Vibriosalmonicida, Xanthomonas campestris, Xenorhabdus nematophilus, Yersiniaenterocolitica, Yersinia pestis, Yersinia pseudotuberculosis, Yersiniamedievalis, and Yersinia ruckeri.

Also provided is a method of treating a disorder associated with QS in amammalian subject resistant to treatment with a standard of careanti-bacterial therapeutic comprising administering to the subject acompound of formula (I) as disclosed herein in an amount effective toinhibit QS in the bacteria causing the infection.

Contemplated bacterial infections include, but are not limited to,bacteremia, septicemia, endo- and pericarditis, sinusitis, woundinfection, burn wounds, upper respiratory tract infection, urinary tractinfection, gastroenteritis, intra-abdominal infections, arthritis,pseudotuberculosis, chronic bronchitis, pneumonia, cerebral, pulmonary,and skin lesions, cerebral and liver abscesses, meningitis, dermatitisor folliculitis, necrotizing fasciitis, cellulitis, urinary tractinfections, Glander's disease, osteomylitis, enterocolitis, contactlens-associated keritis, and conjunctivitis. The treatment may also beused to treat infections immunocompromised individuals, such as thosewith cancer and acquired immunodeficiency syndrome (AIDS). Thesecompounds may also be useful in treating disorders associated withbiofilm formation in patients with cystic fibrosis, dental caries,periodonitis, otitis media, muscular skeletal infections, necrotizingfasciitis, biliary tract infection, osteomyelitis, bacterialprostatitis, endocarditis, native valve endocarditis, cystic fibrosispneumonia, infections associated with chronic granulomatous, meloidosis,or skin lesions associated with bullous impetigo, atopic dermatitis andpemphigus foliaceus or implanted device-related infections. It may alsobe used to treat nosocomial infections including pneumonia, infectionassociated with sutures, exit sites, arteriovenous sites, scleralbuckles, contact lenses, urinary catheter cystitis peritoneal dialysisperitonitis, IUDs, endotracheal tubes, Hickman catheters, central venouscatheters, mechanical heart valves, vascular grafts, biliary stentblockage, and orthopedice devices.

Combination Therapy

The methods of the embodiments also include the use of a compound orcompounds as described herein together with one or more additionaltherapeutic agents for the treatment of disease conditions. Thus, forexample, the combination of active ingredients may be: (1) co-formulatedand administered or delivered simultaneously in a combined formulation;(2) delivered by alternation or in parallel as separate formulations; or(3) by any other combination therapy regimen known in the art. Whendelivered in alternation therapy, the methods described herein maycomprise administering or delivering the active ingredientssequentially, e.g., in separate solution, emulsion, suspension, tablets,pills or capsules, or by different injections in separate syringes. Ingeneral, during alternation therapy, an effective dosage of each activeingredient is administered sequentially, i.e., serially, whereas insimultaneous therapy, effective dosages of two or more activeingredients are administered together. Various sequences of intermittentcombination therapy may also be used.

In some cases, a compound disclosed herein is administered and/orformulated with a second therapeutic—e.g., an antibacterial agent.

Antibacterial agents contemplated for use include, without limitation,antibiotics of the β-lactam group such as natural penicillins,semisynthetic penicillins, natural cephalosporins, semisyntheticcephalosporins, cephamycins, 1-oxacephems, clavulanic acids, penems,carbapenems, nocardicins, monobactams; tetracyclines,anhydrotetracyclines, anthracyclines; aminoglycosides; nucleosides suchas N-nucleosides, C-nucleosides, carbocyclic nucleosides, blasticidin S;macrolides such as 12-membered ring macrolides, 14-membered ringmacrolides, 16-membered ring macrolides; ansamycins; peptides such asbleomycins, gramicidins, polymyxins, bacitracins, large ring peptideantibiotics containing lactone linkages, actinomycins, amphomycin,capreomycin, distamycin, enduracidins, mikamycin, neocarzinostatin,stendomycin, viomycin, virginiamycin; cycloheximide; cycloserine;variotin; sarkomycin A; novobiocin; griseofulvin; chloramphenicol;mitomycins; fumagillin; monensins; pyrrolnitrin; fosfomycin; fusidicacid; D-(p-hydroxyphenyl)glycine; D-phenylglycine; enediynes;benzylpenicillin (potassium, procaine, benzathine),phenoxymethylpenicillin (potassium), phenethicillin potassium,propicillin, carbenicillin (disodium, phenyl sodium, indanyl sodium),sulbenicillin, ticarcillin disodium, methicillin sodium, oxacillinsodium, cloxacillin sodium, dicloxacillin, flucloxacillin, ampicillin,mezlocillin, piperacillin sodium, amoxicillin, ciclacillin, hectacillin,sulbactam sodium, talampicillin hydrochloride, bacampicillinhydrochloride, pivmecillinam, cephalexin, cefaclor, cephaloglycin,cefadroxil, cephradine, cefroxadine, cephapirin sodium, cephalothinsodium, cephacetrile sodium, cefsulodin sodium, cephaloridine,cefatrizine, cefoperazone sodium, cefamandole, vefotiam hydrochloride,cefazolin sodium, ceftizoxime sodium, cefotaxime sodium, cefinenoximehydrochloride, cefuroxime, ceftriaxone sodium, ceftazidime, cefoxitin,cefinetazole, cefotetan, latamoxef, clavulanic acid, imipenem,aztreonam, tetracycline, chlortetracycline hydrochloride,demethylchlortetracycline, oxytetracycline, methacycline, doxycycline,rolitetracycline, minocycline, daunorubicin hydrochloride, doxorubicin,aclarubicin, kanamycin sulfate, bekanamycin, tobramycin, gentamycinsulfate, dibekacin, amikacin, micronomicin, ribostamycin, neomycinsulfate, paromomycin sulfate, streptomycin sulfate, dihydrostreptomycin,destomycin A, hygromycin B, apramycin, sisomicin, netilmicin sulfate,spectinomycin hydrochloride, astromicin sulfate, validamycin,kasugamycin, polyoxin, blasticidin S, erythromycin, erythromycinestolate, oleandomycin phosphate, tracetyloleandomycin, kitasamycin,josamycin, spiramycin, tylosin, ivermectin, midecamycin, bleomycinsulfate, peplomycin sulfate, gramicidin S, polymyxin B, bacitracin,colistin sulfate, colistinmethanesulfonate sodium, enramycin, mikamycin,virginiamycin, capreomycin sulfate, viomycin, enviomycin, vancomycin,actinomycin D, neocarzinostatin, bestatin, pepstatin, monensin,lasalocid, salinomycin, amphotericin B, nystatin, natamycin,trichomycin, mithramycin, lincomycin, clindamycin, clindamycin palmitatehydrochloride, flavophospholipol, cycloserine, pecilocin, griseofulvin,chloramphenicol, chloramphenicol palmitate, mitomycin C, pyrrolnitrin,fosfomycin, fusidic acid, bicozamycin, tiamulin, or siccanin. In somecases, the second therapeutic agent blocks virulence products. In suchcases, the bacteria is prevented from secreting its virulence factors(toxins etc.) and the immune system can clear the bacteria. See, e.g.,Lin et al., Arch Biochem Biophys. 2010 Sep. 15; 501(2):214-20. Epub 2010Jun. 15; Darby et al., J Antimicrob Chemother. 2010 July; 65(7):1424-7.Epub 2010 Apr. 30; Bryk et al, Biochemistry. 2010 Mar. 2; 49(8):1616-27;Lin et al., Nature. 2009 Oct. 1; 461(7264):621-6. Epub 2009 Sep. 16; deCarvalho et al., J Med Chem. 2009 Oct. 8; 52(19):5789-92; Nathan et al.,Tuberculosis (Edinb). 2008 August; 88 Suppl 1:S25-33; Bryk, et al., CellHost Microbe. 2008 Mar. 13; 3(3):137-45; Casenghi, et al., PLoS Med.2007 Nov. 6; 4(11):e293; Hu et al., Mol Microbiol. 2006 March;59(5):1417-28; and Kline et al., J Med Chem. 2008 Nov. 27;51(22):7065-74.

Further contemplated are antibacterial agents selected fromacedisulfone, aceturate, acetyl sulfametossipirazine, acetylsulfamethoxypyrazine, acranil, albendazole, alexidine, amatadine,ambazone, amdinocillin, amikacin, p-aminosalicyclic acid hydrazine,amoxicillin, ampicillin, anisomycin, apalcillin, apicyclin, apramycin,arbekacin, argininsa, aspoxicillin, azidamfenicol, azidocillin,azithromycin, azlocillin, aztreonam, bacampicillin, benzoylpas, benzylpenicillin acid, benzyl sulfamide, bicozamycin, bipenam, brodimoprim,capreomycin, carbenicillin, carbomycin, cafazedone, carindacillin,carumonam, cefcapene pivoxil, cefaclor, cefazedone, cefazolin,cefbuperazone, cefclidin, cefdinir, cefditoren, cefixime, cefinenoxime,cefmetazole, cefminox, cefodizime, cefonicid, cefoperazone, ceforanide,cefotaxime, cefotetan, cefotiam, cefoxitin, cefozopran, cefpimizole,cefpriamide, cefpirome, cefpodoxime proxetil, cefprozil, cefroxadine,cefsulodin, ceftazidime, cefteram, ceftezole, ceftibuten, ceftiofur,ceftizoxime, ceftriaxone, cefuroxime, cefuzonam, cephacetrile sodium,cephadrine, cephalexin, cephaloglycin, cephaloridine, cephalosporin C,cephalothin, cephapirin sodium, cephradine, chloramphenicol,chlorotetracycline, cinoxacin, ciprofloxacin, claritromycin, clavulanicacid, clinafloxacin, clindamycin, clofazimine, clofoctal, clometocillin,clomocycline, cloxacillin, cloxyquin, cyclacilline, cycloserine,danoflaxcin, dapsone, deoxycycline, deoxydihydrostreptomycin, dibekacin,dicloxacillin, difloxacin, dihydro streptomycin, dimetridazole,diminazene, dirirtomycin, doripenam, eflornithine, enoxacin,enrofloxacin, enviomycin, epicillin, erythromycin, etacillin,ethambutol, ethionamide, famciclovir, fenbecillin, fleroxacin, flomoxef,floxacillin, flumequine, furonazide, fortimycin, furazolium chloride,gentamycin, glyconiazide, grepafloxacin, guamecycline, halofuginone,hetacillin, homidium, ipronidazole, isoniazide, iosamycin, inosine,lauroguadine, lenampicillin, levofloxin, lincomycin, lomefloxacin,loracarbef, lymecyclin, mafenide, mebendazole, meclocyclin, meropenem,metampicillin, metacicline, methacycline, methicillin sodium,metronidazole, 4′-(methylsulfamoyl) sulfanilanilide, mezlocillin,meziocillin, micronomycin, midecamycin A₁, minocycline, miocamycin,miokamycin, morfazinamide, moxalactam, mupirocin, myxin, nadifloxacin,nalidixic acid, negramycin, neomycin, netlimycin, nifurfoline,nifurpirinol, nifurprazine, nimorazole, nitroxoline, norfloxacin,novobiocin, ofloxacin, oleandomycin, opiniazide, oxacillin,oxophenarsine, oxolinic acid, oxytetracycline, panipenam, paromycin,pazufloxacin, pefloxacin, penicillin G potassium salt, penicillin N,penicillin O, penicillin V, penethamate hydroiodide, pentamidine,phenamidine, phenethicillin potassium salt, phenyl aminosalicyclate,pipacycline, pipemidic acid, piperacillin, pirlimycin, piromidic acid,pivampicillin, pivcefalexin, profiromycin, propamidine, propicillin,protionamide, puraltadone, puromycin, pyrazinamide, pyrimethamine,quinacillin, quinacrine, quinapyramine, quintine, ribostamycin,rifabutine, rifamide, rifampin, rifamycin, rifanpin, rifapentine,rifaxymine, ritipenem, rokitamycin, rolitetracycline, rosamycin,rufloxacin, salazosulfadimidine, salinazid, sancycline, sarafloxacin,sedacamycin, secnidazole, sisomycin, sparfloxacin, spectinomycin,spiramycin, spiramycin I, spiramycin II, spiramycin III, stilbamidine,streptomycin, streptonicizid, sulbactam, sulbenicillin, succisulfone,sulfanilamide, sulfabenzamide, sulfacetamide, sulfachloropyridazine,sulfachrysoidine, sulfacytine, sulfadiazine, sulfadicramide,sulfadimethoxin, sulfadoxine, sulfadrazine, sulfaetidol, sulfafenazol,sulfaguanidine, sulfaguanole, sulfalene, sulfamerazine, sulfameter,sulfamethazine, sulfamethizole, sulfamethomidine, sulfamethoxazole,sulfamethoxypyridazine, sulfamethylthiazol, sulfamethylthiazole,sulfametrole, sulfamidochrysoidine, sulfamoxole, sulfanilamide,4-sulfanilamido salicylic acid, 4-4′-sulfanilybenzylamine,p-sulfanilylbenzylamine, 2-p-sulfinylanilinoethanol, sulfanilylurea,sulfoniazide, sulfaperine, sulfaphenazole, sulfaproxyline,sulfapyrazine, sulfappidine, sulfathiazole, sulfaethidole,sulfathiourea, sulfisomidine, sulfasomizole, sulfasymazine,sulfisoxazole, 4,4′-sulfinyldianiline, N⁴-sulfanilylsulfanilamide,N-sulfanilyl-3,4-xylamide, sultamicillin, talampicillin, tambutol,taurolidine, teiclplanin, temocillin, tetracycline, tetroxoprim,thiabendazole, thiazolsulfone, tibezonium iodide, ticarcillin,tigemonam, tinidazole, tobramycin, tosufloxacin, trimethoprim,troleandromycin, trospectomycin, trovafloxacin, tubercidine, miokamycin,oleandomycin, troleandromycin, vancomycin, verazide, viomycin,virginiamycin, and zalcitabine.

The invention will be more fully understood by reference to thefollowing examples which detail exemplary embodiments of the invention.They should not, however, be construed as limiting the scope of theinvention. All citations throughout the disclosure are hereby expresslyincorporated by reference.

EXAMPLES Example 1 Materials and Methods

5-(Propylthiomethyl)pyrrolidin-2-one [7a(5S)]. Procedure A. Propanethiol(50 μL, 42 mg, 0.55 mmol) was added dropwise to a stirred suspension ofNaH (35 mg, 0.875 mmol, 60%/mineral oil) in dry DMF (1 mL) under Aratmosphere at 0° C. After 10 min (till gas evolution has ceased),solution of compound 6 (17) [(5S), 82 mg, 0.46 mmol] in dry DMF (1 mL)was added dropwise, and after 15 min the reaction mixture was allowed towarm to ambient temperature. After 12 h the resulting mixture wasquenched with water at 0° C., volatiles were evaporated, and the residuewas column chromatographed (EtOAc→10% MeOH/EtOAc) to give 7a(5S) (77 mg,96%) as a colorless oil: ¹H NMR δ 0.98 (t, J=7.3 Hz, 3H), 1.60 (sx,J=7.3 Hz, 2H), 1.76-1.87 (m, 1H), 2.25-2.34 (m, 1H), 2.34-2.45 (m, 2H),2.52 (t, J=7.3 Hz, 2H), 2.54 (dd, J=7.7, 13.2 Hz, 1H), 2.68 (dd, J=5.5,13.2 Hz, 1H), 3.80 (‘quint’, J=5.5 Hz, 1H), 6.73 (br. s, 1H); ¹³C NMR δ13.4, 23.1, 26.6, 30.2, 34.7, 38.6, 53.9, 178.0; MS (APCI) m/z 174(MH⁺). HRMS (AP-ESI) m/z calcd for C₈H₁₅NNaOS [M+Na]⁺ 196.0772. found196.0779.

N-tert-Butoxycarbonyl-5-(propylthiomethyl)pyrrolidin-2-one [8a(5S)].Procedure B. DMAP (114 mg, 0.93 mmol), and (Boc)₂O (398 mg, 1.82 mmol)were added to a stirred solution of compound 7a (77 mg, 0.445 mmol) inCH₂Cl₂ (2 mL) at ambient temperature under Ar atmosphere. After 48 h,the reaction mixture was quenched with H₂O (5 mL) and partitionedbetween CH₂Cl₂//NaHCO₃/H₂O. The organic layer was washed (brine), dried(MgSO₄) and evaporated. The residue was column chromatographed (30→40%EtOAc/hexane) to give 8a (5S) (107 mg, 88%) as a colorless oil: ¹H NMR δ0.95 (t, J=7.3 Hz, 3H), 1.50 (s, 9H), 1.58 (sx, J=7.3 Hz, 2H), 1.96-2.04(m, 1H), 2.06-2.17 (m, 1H), 2.40 (ddd, J=2.6, 9.6, 17.9 Hz, 1H), 2.50(“dt”, J=4.9, 7.3 Hz, 2H), 2.58-2.67 (m, 1H), 2.60 (dd, J=9.2, 13.5 Hz,1H), 2.86 (ddd, J=0.5, 2.8, 13.5 Hz, 1H), 4.20-4.27 (m, 1H); ¹³C NMR δ13.3, 21.9, 23.1, 28.0, 31.2, 34.8, 35.4, 57.5, 83.1, 149.8, 174.2; MS(ESI) m/z 274 (10, MH⁺), 215 (100, [MH-59]⁺).

5-(Propylthiomethyl)pyrrolidin-2-ol [10a(5S)]. Procedure C. LiEt₃BH (1Msoln in THF, 0.98 mL, 0.98 mmol) was added to a stirred solution of 8a(107 mg, 0.39 mmol) in CH₂Cl₂ (3 mL) at −78° C. under N₂ atmosphere.After 30 min, the reaction mixture was quenched with MeOH (4 mL) and wasallowed to warm to ambient temperature. Volatiles were evaporated andthe residue was partitioned (EtOAc//NaHCO₃/H₂O), washed (brine) anddried (MgSO₄). The resulting oil was chromatographed (30→40%EtOAc/hexane) to giveN-tert-butoxycarbonyl-5-(propylthiomethyl)pyrrolidin-2-ol [9a(5S); 104mg, 96%] as a colorless oil of the mixture of anomers/rotamers: MS (ESI)m/z 274 (10, [M−1]⁺), 258 (100, [M−17]⁺). Procedure D. Compound 9a (104mg, 0.37 mmol) in TFA (4.0 mL) was stirred at rt for 2 h. Volatiles wereevaporated to give 10a (62 mg, 96%) as a light yellow oil of a mixtureof isomers accompanied by ˜25% of the open aldehyde form [¹H NMR δ 8.89(s, ˜0.25H); and ¹³C NMR δ 180.8]; MS (ESI) m/z 158 (100, [M−17]⁺).

Structure of compound 10a was additionally confirmed by conversion tothe corresponding O-benzyloxime derivative with benzylhydroxylaminehydrochloride (6 equiv.) in anhydrous pyridine: MS (ESI) m/z 281 (60,MH⁺), 158 (100, [M-BnONH]⁺), (APCI) m/z 281 (100, MH⁺).

N-(tert-Butoxycarbonyl)-3,4-dihydroxy-3,4-O-isopropylidene-5-[(methanesulfonyloxy)methyl]pyrrolidin-2-one[13(3R,4R,5R)]. Step a. Triethylamine (93 μL, mg, 67 mg, 0.66 mmol) andMsCl (25 μL, 38 mg, 0.33 mmol) were added dropwise to stirred solutionof 11 (20) (60 mg, 0.22 mmole) in anhydrous CH₂Cl₂ (6 mL) at 0° C.(ice-bath). After 5 min, ice-bath was removed and the reaction mixturewas allowed to stir at ambient temperature for 30 min. The reactionmixture was quenched with saturated NaHCO₃/H₂O and was extracted withCH₂Cl₂ The organic layer was washed (brine), dried (MgSO₄) andevaporated to giveN-tert-butoxycarbonyl-1,4-dideoxy-1,4-imino-2,3-O-isopropylidene-5-O-methanesulfonyl-D-ribitol12 (73 mg, 96%) as a mixture (˜3:2) of two rotamers of sufficient purityto be directly used for next step (see SI for spectral data). Step b.RuO₂×H₂O (8.5 mg, 0.064 mmol) was added to a stirred solution of NaIO₄(172 mg, 0.96 mmol) in H₂O (1 mL) at ambient temperature. After 5 min, asolution of 12 (80 mg, 0.32 mmol) in EtOAc (1 mL) was added dropwise andthe reaction mixture was continued to stir for 12 h. H₂O (20 mL) andEtOAc (20 mL) were added and the separated aqueous layer was furthermoreextracted with EtOAc (2×20 mL). The combined organic layers were washed(brine), dried (MgSO₄) and evaporated. The residue was columnchromatographed (EtOAc) to give 13 (78 mg, 95%) as a colorless oil: ¹HNMR δ 1.37 (s, 3H), 1.44 (s, 3H), 1.54 (s, 9H), 3.01 (s, 3H), 4.39-4.43(‘m’, 2H), 4.58 (d, J=5.45 Hz, 1H), 4.64 (dd, J=11.2, 3.1 Hz, 1H), 4.70(d, J=5.45 Hz, 1H); ¹³C NMR δ 25.6, 27.0, 28.0, 37.7, 59.2, 67.0, 74.5,77.5, 84.7, 112.8, 149.7, 170.2; MS (APCI) m/z 298 (100,[MH₂-Boc+MeOH]⁺).

N-(tert-Butoxycarbonyl)-3,4-dihydroxy-3,4-O-isopropylidene-5-(hexylthiomethyl)pyrrolidin-2-one[14 (3R,4R,5S)]. Treatment of 13 (60 mg, 0.16 mmol] in dry DMF (0.5 mL)with sodium hexathiolate [generated from hexanethiol (46.8 μL, 0.33mmol)/NaH (14 mg, 0.35 mmol, 60%/mineral oil) in dry DMF (0.5 mL)] byProcedure A [column chromatography (5%→10% MeOH/EtOAc)] gave 14 (25 mg,40%) as a colorless oil and N-Boc deprotected 14 (24 mg, 38%) as a whitecrystalline solid. Compound 14 had: ¹H NMR δ 0.81 (t, J=7.0 Hz, 3H),1.16-1.27 (m, 6H), 1.30 (s, 3H), 1.39 (s, 3H), 1.44-1.59 (m, 11H),2.36-2.50 (m, 2H), 2.76 (dd, J=6.2, 14.4 Hz, 1H), 2.82 (dd, J=2.7, 14.4Hz, 1H), 4.31 (dd, J=2.7, 6.2 Hz, 1H), 4.38 (d, J=5.5 Hz, 1H), 4.78 (d,J=5.5 Hz, 1H); ¹³C NMR δ 14.0, 22.5, 25.5, 27.0, 28.0, 28.3, 29.6, 31.3,33.7, 33.9, 60.8, 76.1, 77.6, 83.9, 112.3, 149.8, 171.0; MS (APCI) m/z288 (100, [MH₂-Boc]⁺). N-Boc deprotected 14 had: ¹H NMR δ 0.88 (t, J=7.0Hz, 3H), 1.25-1.36 (m, 6H), 1.38 (s, 3H), 1.48 (s, 3H), 1.56-1.62 (m,2H), 2.52-2.75 (m, 3H), 2.73 (dd, J=5.9, 13.4 Hz, 1H), 3.81 (‘t’, J=6.1Hz, 1H), 4.50 (d, J=5.9 Hz, 1H), 4.69 (d, J=5.9 Hz, 1H), 5.94 (s, 1H);¹³C NMR δ 14.0, 29.7, 22.5, 28.5, 31.4, 25.6, 26.9, 33.2, 33.7, 58.0,76.6, 79.2, 112.7, 173.2; MS (APCI) m/z 288 (100, MH⁺).

3,4-Dihydroxy-5-(hexylthiomethyl)pyrrolidin-2-one [16(3R,4R,5S)].TFA/H₂O (1 mL, 9:1) was added to 14 or N-Boc deprotected 14 (22 mg, 0.07mmol) and the resulting solution was stirred at 0° C. for 3 h.Evaporation of volatiles gave light yellow oil that was columnchromatographed (5→10% MeOH/EtOAc) to give 16 (12 mg, 63%) as acolorless oil: ¹H NMR δ 0.87 (t, J=7.0 Hz, 3H), 1.24-1.39 (m, 6H),1.52-1.59 (m, 2H), 2.50-2.55 (m, 3H), 2.73 (dd, J=5.5, 13.6 Hz, 1H),3.71 (‘t’, J=6.4 Hz, 1H), 4.21 (d, J=5.0 Hz, 1H), 4.44 (d, J=5.0 Hz,1H), 7.11 (s, 1H); ¹³C NMR δ 14.0, 29.6, 14.1, 22.5, 31.4, 32.7, 35.3,59.9, 69.8, 71.8, 176.0; MS (APCI) m/z 248 (100, MH⁺).

3,4-Dihydroxy-5-(hexylthiomethyl)pyrrolidin-2-ol [20(3R,4R,5S)].Treatment of 14 (40 mg, 0.1 mmol) in THF (1 mL) with LiEt₃BH (1M/THF,0.26 mL, 0.26 mmol), by procedure C [column chromatography (10→20%EtOAc/hexane)] gaveN-(tert-butoxycarbonyl)-3,4-dihydroxy-3,4-O-isopropylidene-5-(hexylthiomethyl)pyrrolidin-2-ol[18 (3R,4R,5S)]; 39 mg, 97%)] as a colorless oil of the mixture ofisomers: MS (ESI) m/z 389 (100, M⁺). Deprotection of 18 (39 mg, 0.1mmol) with TFA/H₂O (0.9:0.1 mL) by Procedure D gave a light yellow oilthat was column chromatographed (5→10% MeOH/EtOAc) to give 20 (22 mg,88%) as a light yellow oil. ¹H NMR showed a mixture of isomersaccompanied by the open aldehyde form. MS (APCI) m/z 230 (40, MH⁺), 232(100, [M−17]⁺).

Synthetic procedures and characterization data for compounds 7b-d, 8b-d,10b-d, 12, 15, 17, and 21 is as follows:

5-(Hexylthiomethyl)pyrrolidin-2-one [7b(5S)]. Treatment of 6 (17) [(5S),823 mg, 4.62 mmol] in dry DMF (6 mL) with a thiolate solution in dry DMF(6 mL) generated from hexanethiol (682 μL, 573 mg, 4.86 mmol), and NaH(204 mg, 5.09 mmol, 60%/mineral oil) by Procedure A [columnchromatography (80% EtOAc/hexane→5% MeOH/EtOAc)] gave 7b(5S) (932 mg,94%) as a colorless oil: ¹H NMR δ 0.90 (t, J=7.0 Hz, 3H), 1.24-1.33 (m,4H), 1.33-1.42 (m, 2H), 1.58 (‘quint’, J=7.4 Hz, 2H), 1.78-1.87 (m, 1H),2.27-2.46 (m, 3H) 2.53 (dd, J=8.0, 13.4 Hz, 1H), 2.54 (t, J=7.3 Hz, 2H),2.70 (dd, J=5.3, 13.2 Hz, 1H), 3.81 (‘quint’, J=6.6 Hz, 1H), 6.47 (br.s, 1H); ¹³C NMR δ 14.0, 22.5, 26.8, 28.5, 29.7, 30.1, 31.4, 32.7, 38.7,53.8, 177.7; MS (ESI) m/z 216 (100, MH⁺).

5-(Nonylthiomethyl)pyrrolidin-2-one [7c(5S)]. Treatment of 6 (17) [(5S),458 mg, 2.58 mmol] in dry DMF (3 mL) with thiolate solution in dry DMF(7 mL) generated from nonanethiol (510 μL, 433 mg, 2.71 mmol), and NaH(114 mg, 2.84 mmol, 60%/mineral oil) in dry DMF (7 mL) by Procedure A[column chromatography (80% EtOAc/hexane→EtOAc)] gave 7c(5S) (652 mg,98%) as a colorless oil: ¹H NMR δ 0.86 (t, J=7.0 Hz, 3H), 1.19-1.29 (m,10H), 1.29-1.38 (m, 2H), 1.54 (‘quint’, J=7.3 Hz, 2H), 1.75-1.85 (m,1H), 2.23-2.43 (m, 3H), 2.51 (t, J=7.5 Hz, 2H), 2.54 (dd, J=7.4, 13.2Hz, 1H), 2.65 (dd, J=5.8, 13.2 Hz, 1H), 3.78 (‘quint’, J=6.5 Hz, 1H),6.97 (br. s, 1H); ¹³C NMR δ 14.1, 22.6, 26.6, 28.8, 29.2, 29.2, 29.4,29.8, 30.1, 31.8, 32.7, 38.6, 53.9, 178.0; MS (ESI) m/z 258 (100, MH⁺).

5-(Dodecylthiomethyl)pyrrolidin-2-one [7d(5S)]. Treatment of 6 (17)[(5S), 448 mg, 2.52 mmol] in dry DMF (3 mL) with thiolate soln in dryDMF (7 mL) generated from dodecanethiol (634 μL, 535 mg, 2.65 mmol), andNaH (110 mg, 2.77 mmol, 60%/mineral oil) in dry DMF (7 mL) by ProcedureA [column chromatography (80% EtOAc/hexane→EtOAc)] gave 7d (5S) (637 mg,85%) as a colorless oil: ¹H NMR δ 0.88 (t, J=7.0 Hz, 3H), 1.21-1.32 (m,16H), 1.32-1.40 (m, 2H), 1.57 (‘quint’, J=7.4 Hz, 2H), 1.77-1.87 (m,1H), 2.26-2.45 (m, 3H), 2.53 (t, J=7.6 Hz, 2H), 2.54 (dd, J=7.8, 13.2Hz, 1H), 2.68 (dd, J=5.4, 13.2 Hz, 1H), 3.80 (‘quint’, J=6.6 Hz, 1H),6.64 (br. s, 1H); ¹³C NMR δ 14.1, 22.7, 26.7, 28.8, 29.2, 29.3, 29.5,29.6, 29.6, 29.6, 29.8, 30.1, 31.9, 32.7, 38.7, 53.8, 177.7; MS (ESI)m/z 300 (100, MH⁺).

N-tert-Butoxycarbonyl-5-(hexylthiomethyl)pyrrolidin-2-one [8b(5S)].Treatment of 7b (311 mg, 1.45 mmol) in CH₂Cl₂ (6 mL) with DMAP (185 mg,1.52 mmol), and (Boc)₂O (746 mg, 3.42 mmol) by procedure B [columnchromatography (20→40% EtOAc/hexane)] gave 8b (5S) (429 mg, 94%) as acolorless oil: ¹H NMR δ 0.89 (t, J=7.0 Hz, 3H), 1.25-1.33 (m, 4H),1.34-1.42 (m, 2H), 1.55 (s, 9H), 1.59 (‘quint’, J=7.4 Hz, 2H), 2.01-2.08(m, 1H), 2.10-2.21 (m, 1H), 2.45 (ddd, J=2.5, 9.6, 17.9 Hz, 1H), 2.56(‘dt’, J=2.9, 7.3 Hz, 2H), 2.62-2.72 (m, 1H), 2.63 (dd, J=9.3, 13.5 Hz,1H), 2.91 (dd, J=2.7, 13.5 Hz, 1H), 4.24-4.31 (m, 1H); ¹³C NMR δ 14.0,22.0, 22.5, 28.1, 28.4, 29.8, 31.2, 31.4, 32.9, 35.5, 57.5, 83.1, 149.8,174.1; MS (ESI) m/z 315 (15, MH⁺), 256 (100, [M−59]⁺).

N-tert-Butoxycarbonyl-5-(nonylthiomethyl)pyrrolidin-2-one [8c(5S)].Treatment of 7c (250 mg, 0.97 mmol) in CH₂Cl₂ (5 mL) with DMAP (125 mg,1.02 mmol), and (Boc)₂O (712 mg, 3.27 mmol) by procedure B [columnchromatography (20→25% EtOAc/hexane)] gave 8c(5S) (345 mg, 99%) as acolorless oil: ¹H NMR δ 0.85 (t, J=7.0 Hz, 3H), 1.19-1.29 (m, 10H),1.29-1.38 (m, 2H), 1.51 (s, 9H), 1.55 (‘quint’, J=7.3 Hz, 2H), 1.96-2.04(m, 1H), 2.06-2.17 (m, 1H), 2.40 (ddd, J=2.5, 9.6, 17.8 Hz, 1H), 2.52(‘dt’, J=3.0, 7.4 Hz, 2H), 2.58-2.67 (m, 1H), 2.60 (dd, J=9.3, 13.5 Hz,1H), 2.86 (dd, J=2.6, 13.5 Hz, 1H), 4.21-4.27 (m, 1H); ¹³C NMR δ 14.0,21.9, 22.6, 28.0, 28.7, 29.1, 29.2, 29.4, 29.8, 31.2, 31.8, 32.9, 35.5,57.5, 83.0, 149.8, 174.0; MS (ESI) m/z 358 (10, MH⁺), 299 (100,[MH-59]⁺).

N-tert-Butoxycarbonyl-5-(dodecylthiomethyl)pyrrolidin-2-one [8d(5S)].Treatment of 7d (234 mg, 0.78 mmol) in CH₂Cl₂ (5 mL) with DMAP (100 mg,0.82 mmol), and (Boc)₂O (600 mg, 2.75 mmol) by procedure B [columnchromatography (15→20% EtOAc/hexane)] gave 8d(5S) (302 mg, 97%) as asolidifying oil: ¹H NMR δ 0.87 (t, 0.1=7.0 Hz, 3H), 1.21-1.31 (m, 16H),1.31-1.40 (m, 2H), 1.53 (s, 9H), 1.58 (‘quint’, J=7.5 Hz, 2H), 1.99-2.06(m, 1H), 2.08-2.20 (m, 1H), 2.43 (ddd, J=2.5, 9.6, 17.9 Hz, 1H), 2.54(‘dt’, J=2.9, 7.4 Hz, 2H), 2.60-2.70 (m, 2H), 2.62 (dd, J=9.2, 13.5 Hz,1H), 2.89 (dd, J=2.6, 13.5 Hz, 1H), 4.23-4.29 (m, 1H); ¹³C NMR δ 14.1,22.0, 22.7, 28.1, 28.8, 29.2, 29.3, 29.5, 29.6, 29.6, 29.6, 29.8, 31.2,31.9, 32.9, 35.5, 57.5, 83.0, 149.8, 174.0; MS (ESI) m/z 400 (10, MH⁺),341 (100, [MH-59]⁺).

5-(Hexylthiomethyl)pyrrolidin-2-ol [10b(5S)]. Treatment of 8b (178 mg,0.56 mmol) in CH₂Cl₂ (3 mL) with LiEt₃BH (1M soln in THF, 1.41 mL, 1.41mmol), by procedure C [quenched with MeOH (4 mL) at low temp., columnchromatography (30→40% EtOAc/hexane)] gaveN-tert-butoxycarbonyl-5-(hexylthiomethyl)pyrrolidin-2-ol [9b(5S); 170mg, 95%)] as a colorless oil of a mixture of isomers: MS (ESI) m/z 316(100, [M−1]⁺), 300 (20, [M−17]⁺). Treatment of 9b with an excess of TFAby Procedure D (step a, 2 h at rt) gave 10b as a light yellow oil as amixture of isomers accompanied by ˜22% of the open aldehyde form [¹H NMRδ 8.91 (s, ˜0.22H)]: MS (ESI) m/z 200 (100, [M−17]⁺). Crude product 10bwas column chromatographed (60→70% EtOAc/hexane) and rechromatographed(0→0.25% MeOH/CHCl₃) to give pure azahemiacetal 10b (α/β, 0.45:1.0; 9.6mg, 13%) as a colorless oil: δ ¹H NMR δ 0.89 (t, J=7.0 Hz, 4.35H),1.26-1.45 (m, 8.7H), 1.47-1.72 (m, 3.9H), 1.75-1.85 (m, 0.45H),1.92-2.07 (m, 3.45H), 2.10-2.23 (m, 0.9H), 2.46 (dd, J=9.5, 13.0 Hz,1H), 2.52-2.65 (m, 2.9H), 2.93-3.02 (m, 0.9H), 3.23 (dd, J=2.5, 13.0 Hz,1H), 3.60-3.68 (m, 1H), 3.67-3.75 (m, 0.45H), 4.04-4.10 (m, 1H),4.20-4.27 (m, 0.45H);

5-(Nonanylthiomethyl)pyrrolidin-2-ol [10c(5S)]. Treatment of 8c (227 mg,0.64 mmol) in CH₂Cl₂ (4 mL) with LiEt₃BH (1M soln in THF, 1.59 mL, 1.59mmol), by procedure C [quenched with MeOH (5 mL) at low temp., columnchromatography (20→30% EtOAc/hexane)] gavetert-Butoxycarbonyl-5-(nonanylthiomethyl)pyrrolidin-2-ol [9c(5S); 220mg, 96%] as a colorless oil of a mixture of isomers: MS (ESI) m/z 358(10, [M−1]⁺), 342 (100, [M−17]⁺). Treatment of 9c with an excess of TFAby Procedure D (step a, 2 h at rt) gave 10c as a light yellow oil of amixture of isomers accompanied by ˜15% of the open aldehyde form [¹H NMRδ 8.87 (s, ˜0.0.15H)]: MS (ESI) m/z 258 (15, [M−1]⁺), 242 (100,[M−17]⁺).

5-(Dodecylthiomethyl)pyrrolidin-2-ol [10d(5S)]. Treatment of 8d (224 mg,0.56 mmol) in CH₂Cl₂ (4 mL) with LiEt₃BH (1M soln in THF, 1.4 mL, 1.4mmol), by procedure C [quenched with MeOH (5 mL) at low temp., columnchromatography (20→30% EtOAc/hexane)] gaveN-tert-butoxycarbonyl-5-(dodecylthiomethyl)pyrrolidin-2-ol [9d(5S); (219mg, 97%)] as a solidifying oil of a mixture of isomers: MS (ESI) m/z 400(5, [M−1]⁺), 384 (100, [M−17]⁺). Treatment of 9d with an excess of TFAby Procedure D (step a, 2 h at rt) gave 10d as light yellow oil as amixture of isomers accompanied by 8% of the open aldehyde form [¹H NMR δ8.89 (s, ˜0.08H)]): MS (ESI) m/z 301 (5, M⁺), 300 (20, [M−1]⁺), 284(100, [M−17]⁺).

N-tert-Butoxycarbonyl-1,4-dideoxy-1,4-imino-2,3-O-isopropylidene-5-O-methanesulfonyl-D-ribitol[12(3R,4R,5R)]. ¹H NMR δ 1.28 (s, 3, CH₃), 1.42 (s, 12H, t-Bu, CH₃),2.96 (s, 1.2, Ms), 2.98 (s, 1.8, Ms), 3.39 (dd, J=12.5, 4.8 Hz, 0.4H),3.46 (dd, J=12.5, 4.8 Hz, 0.6H), 3.69 (d, J=12.5 Hz, 0.6H), 3.82 (d,J=12.5 Hz, 0.4H), 4.10-4.14 (m, 0.4H), 4.22-4.30 (m, 1H), 4.22-4.29 (m,1.4H), 4.45 (dd, J=10.1, 4.1 Hz, 0.6H), 4.65 J=5.9 Hz, 1H); 4.72 (‘t’,J=5.3 Hz, 1H); ¹³C NMR (major rotamer) δ 24.9, 26.9, 29.6, 37.1, 52.5,62.4, 68.9, 79.2, 80.4, 81.7, 112.1, 154.2; ¹³C NMR (minor rotamer) δ24.9, 26.9, 29.6, 37.5, 53.1, 62.6, 68.6, 78.5, 80.6, 82.5, 112.1,153.6; MS (APCI) m/z 352 (10, MH⁺), 252 (100, [MH₂-Boc]⁺).

N-(tert-Butoxycarbonyl)-3,4-dihydroxy-3,4-O-isopropylidene-5-(nonylthiomethyl)pyrrolidin-2-one[15(3R,4R,5S)]. Treatment of 13 (60 mg, 0.16 mmol] in dry DMF (0.5 mL)with nonathiolate [generated from nonanethiol (62 μL, 0.33 mmol)/NaH (14mg, 0.35 mmol, 60%/mineral oil) in dry DMF (0.5 mL)] by Procedure A(column chromatography 5%→10% MeOH/EtOAc) gave 15 (30 mg, 42%) as acolorless oil: ¹H NMR δ 0.87 (t, J=7.0 Hz, 3H), 1.25-1.31 (m, 12H), 1.36(s, 3H), 1.45 (s, 3H), 1.56-1.57 (m, 11H), 2.44-2.54 (m, 2H), 2.82 (dd,J=6.2, 14.4 Hz, 1H), 2.91 (dd, J=2.7, 14.4 Hz, 1H), 4.38 (dd, J=2.7, 6.2Hz, 1H), 4.45 (d, J=5.5 Hz, 1H), 4.85 (d, J=5.5 Hz, 1H); ¹³C NMR δ 14.1,22.6, 28.7, 29.2, 29.2, 29.4, 31.8, 29.7, 24.4, 25.5, 27.0, 28.0, 33.7,33.9, 60.8, 76.1, 77.6, 83.9, 112.3, 149.8, 170.6; MS (APCI) m/z m/z 330(100, [MH₂-Boc]⁺).

3,4-Dihydroxy-5-(nonylthiomethyl)pyrrolidin-2-one [17(3R,4R,5S)].Treatment of 15 (20 mg, 0.04 mmol) with TFA/H₂O (1 mL, 9:1), asdescribed for 16, gave 17 (10 mg, 85%) as a colorless oil. ¹H NMR δ 0.88(t, J=6.8 Hz, 3H), 1.20-1.38 (m, 12H), 1.52-1.59 (m, 2H), 2.49-2.54 (m,3H), 2.70 (dd, J=5.4, 13.5 Hz, 1H), 3.71 (‘t’, J=5.6 Hz, 1H), 4.25 (d,J=4.9 Hz, 1H), 4.49 (d, J=4.6 Hz, 1H), 7.15 (s, 1H); ¹³C NMR δ 14.1,22.7, 28.8, 29.2, 29.3, 29.7, 31.9, 29.5, 27.0, 32.6, 35.0, 60.7, 69.7,72.5, 176.2; MS (APCI) m/z 290 (100, [MH]⁺).

3,4-Dihydroxy-5-(nonylthiomethyl)pyrrolidin-2-ol [21(3R,4R,5S)].Treatment of 15 (40 mg, 0.09 mmol) in THF (1 mL) with LiEt₃BH (1M/THF,0.22 mL, 0.22 mmol), by procedure C [column chromatography (10→20%EtOAc/hexane)] gaveN-(tert-butoxycarbonyl)-3,4-dihydroxy-3,4-O-isopropylidene-5-nonylthiomethyl-pyrrolidine-2-ol[19(3R,4R,5S)]; 30 mg, 75%)] as a colorless oil as a mixture of isomers:MS (APCI) m/z 414 (100, [M−17]⁺), 314 (95. [MH-Boc-17]⁺). Deprotectionof 19 (28 mg, 0.06 mmol) with an excess of TFA/H₂O (0.9:0.1 mL) byProcedure D gave a light yellow oil that was column chromatographed(5→10% MeOH/EtOAc) to give 21 (18 mg, 96%) as a light yellow oil. ¹H NMRshowed a complex mixture of isomers: MS (APCI) m/z 292 (100, MH⁺), 274(60, [M−17]⁺).

Biological Assays:

Anti-Quorum Sensing Assay (β-Galactosidase Assay). An overnight (O/N)culture of Escherichia coli DH5α harboring the plasmids pSC11, whichcontains a P_(lasI)-lacZ translational fusion (24), and pJN105L, whichcontains a P_(BAD)-lasR expression plasmid (25) grown in LB media (10 gtryptone, 5 g yeast extract, 5 g sodium chloride per liter) supplementedwith ampillicin (100 μg/ml) and gentamycin (15 μg/ml), was diluted to anOD₆₀₀ of 0.150. At this time, arabinose (0.2% w/v),N-3-(oxododecanoyl)homoserine lactone (3-oxo-C₁₂-AHL; 2 μM), and eitherthe compound under analysis or solvent (DMSO), was added to the culture(1.5 mL). A negative control containing only solvent and arabinose (0.2%w/v) was also assayed. The cultures were incubated with shaking forthree hours at 37° C.

The conditions for the rhl biomonitor Escherichia coli DH5α harboringpECP61.5 plasmid, which contains P_(tac)-rhlR and P_(rhlΛ)-lacZ (4),were essentially same except that the LB medium was only supplementedwith ampillicin (100 μg/ml), the O/N culture was diluted to an OD₆₀₀ of0.150, induced with 1 mM IPTG, 2 μM C₄-HSL and the compounds or thecontrols added when the OD₆₀₀ reached 1.0. After incubation at 37° C.for 4 hours with shaking, β-galactosidase activity was assayed asdescribed previously (28). Miller units were calculated as described(29). Assays were repeated at least twice. For each biologicalreplicate, experimental triplicates were performed and the averagepercent activity calculated by dividing the average Miller units fromthe samples containing compound or extract by the average Miller unitsfrom the sample containing solvent and multiplying by 100. Significanceof inhibition was determined using a paired two-tailed Student t-test.

Luminescence Assay: Vibrio harveyi was grown in AB medium. A 2.5 mLaliquot of overnight culture of V. harveyi was added to 2.5 μL and 10 μLof each compound as well as the solvent. The compound was dissolved inwater or DMSO to serve as a control. Growth and luminescence weremeasured simultaneously in a modified Spec20 for three hours. Growth wasmeasured as OD₆₀₀ and luminescence was recorded in light units (1LU=6.51×10⁸ quanta/sec/mL).

Strains: E. coli DH5α harboring a P_(BAD)-lasR expression plasmid and aP_(lasI)-lacZ translational fusion plasmid was used as a biomonitor forthe P. aeruginosa Las QS system, and e. coli XL-1Blue harboring aplasmid containing rhlA::lacZ translational fusion and P_(tac)-rhlR wasused as a biomonitor for the P. aeruginosa Rhl QS system. V. harveyistrain B392 (MAV) was used.

Example 2 Substituted Lactam and Cyclic Azahemiacetals ModulatePseudomonas aeruginosa Quorum Sensing

In this work, a set of optically pure γ-lactams and their reduced cyclicazahemiacetal analogues were synthesized, bearing the additionalalkylthiomethyl substituent, and evaluated their effect on P. aeruginosaAHL-dependent las and rhl QS pathways. The concentration of theseligands and the simple structural modification such as the length of thealkylthio substituent has notable effect on activity. The γ-lactamderivatives with nonanylthio or dodecylthio chains acted as inhibitorsof las signaling with moderate potency. The cyclic azahemiacetal withshorter propylthio or hexylthio substituent was found to stronglyinhibit both las and rhl signaling at higher concentrations while thepropylthio analogue strongly stimulated the las QS system at lowerconcentrations (50 μg/mL).

Design and Synthesis. The (S)-5-(bromomethyl)pyrrolidin-2-one (6), a keysubstrate for the synthesis of γ-lactam analogue 7 was convenientlyprepared from L-pyroglutamic acid (17). Displacement of bromide in 6with sodium propanethiolate produced5(S)-(propylthiomethyl)pyrrolidin-2-one (7a, 96%; Scheme 1). Since itwas previously demonstrated that the length of the side chain is crucialfor determining the agonistic and antagonistic activity (18), lactamscontaining C6, C9 and C12 alkylthio chain lengths (7b-d) were alsoanalogously prepared. A set of the cyclic azahemiacetals (N,O-acetals orhemiaminals) 10 with a hydroxyl group instead of a carbonyl oxygen at C2was synthesized as well. Thus, although, attempted reduction of lactams(7) with LiBEt₃H was unsuccessful, reduction of the N-Boc protectedlactams 8a-d proceeded smoothly to afford azahemiacetals 9a-d.Subsequent deprotection with trifluoroacetic acid afforded5(S)-(alkylthiomethyl)pyrrolidin-2-ol 10a-d as a mixture of isomers.

To increase the polarity/solubility of the lactam and azahemiacetalanalogues in the testing media, aza analogues with hydroxyl groups at C3and C4 were also prepared. The N-Boc protected1,4-dideoxy-1,4-imino-D-ribitol (11) (19-21), conveniently prepared fromD-gulonic-g-lactone, served as a suitable starting material for thesynthesis of dihydroxy γ-lactams 14 and 15. Thus, mesylation of ribitol11 followed by the selective oxidation (22) of the resulting 12 afforded13. Displacement of the mesylate 13 with sodium hexane- andnonanethiolate produced 5-alkylthiomethyl lactams 14 and 15 in highyields which were deprotected with TFA to give (5S)-(hexyl- ornonanylthiomethyl)-3,4-dihydroxypyrrolidin-2-ones 16 and 17 (Scheme 2).Reduction of 5-alkylthiomethyl lactams 14 and 15 with LiBEt3H affordedcyclic azahemiacetals 18 and 19. Subsequent deprotection with TFAprovided (5S)-(alkylthiomethyl)-3,4-dihydroxypyrrolidin-2-ols 20 and 21as a complex mixture of azahemiacetals existing in equilibrium withdehydrated form (imine) as well as with open aldehyde and dimeric forms,as reported for such class of 4-azaribofuranoses (23). Theseazahemiacetals can be considered as aza analogues ofS-ribosyl-L-homocysteine (SRH) in which (a) ribose oxygen is replaced bynitrogen atom and (b) the homocysteine moiety is substituted withn-alkylthiols with different length of carbon chain.

Screening against las signaling. To determine the effect of the lactams(7, 16, and 17) and the cyclic azahemiacetal derivatives (10, 20 and 21)on the P. aeruginosa las AHL-mediated pathway, a las-dependentβ-galactosidase reporter (P_(las)I-lacZ) was expressed with lasR in E.coli (24-25). As expected, and in agreement with published data (24-25),exogenous 3-oxo-C₁₂-AHL activated the P_(lasI)-lacZ (FIG. 2). Also, noactivity was observed in absence of exogenous AHL. The effect ofsynthetic compounds on the las activity was also compared with theaddition of DMSO as a solvent. The propylthio lactam 7a and itsazahemiacetal counterpart 10a were initially screened at a concentrationof 100 μg/mL for their activity against the las system. The lactam 7ainhibited las activity approximately by 28%, while the azahemiacetal 10awas found to enhance las reporter activity by 15%. This was dependentupon the addition of 2 μM of 3-oxo-C₁₂-AHL. However, azahemiacetal 10asignificantly stimulated (approximately by 2.3-fold) las reporteractivity at the concentration of 50 μg/mL, while inhibiting las reporteractivity by 69% and 89% at 150 and 200 μg/mL, respectively. In contrast,the lactam analogue 7a inhibited las activity at all concentrationstested. Cell growth was not inhibited by the addition of lactam andazahemiacetal compounds at the tested concentrations (data not shown).

Among other lactam analogues tested, the percent inhibition increased ina concentration dependent manner. Inhibition potency also increased asthe alkylthio chain length increased. Specifically, nonylthio lactam 7cand dodecylthio lactam 7d were found to possess greatest inhibition atall concentrations tested. At the lowest concentration tested (50μg/mL), nonylthio lactam 7c inhibited 28% while dodecylthio lactam 7dinhibited 48%. On the contrary, among the cyclic azahemiacetalsanalogues, no general trend was observed between chain length andpercent inhibition. As with the propylthio azahemiacetal 10a, hexylthioazahemiacetal 10b also stimulated QS at 50 μg/mL but with much lesserpotency and inhibited 100% at all higher concentrations tested.Azahemiacetals containing nonyl side chain 10c and dodecyl chain 10dshowed moderate activity. The ribolactam analogues 16 and 17 and theircyclic azahemiacetal counterparts 20 and 21 were found to inhibit lasactivity at all concentrations tested but only with moderate potencywith azahemiacetals being slightly more active.

TABLE 1 Effect of lactam and cyclic azahemiacetal analogues on rhlsignaling Concentration (μg/mL) 50 100 150 200 Compound PercentActivity^(a,b) ± Standard Deviation  7a 104 ± 24  118 ± 0.8 104 ± 13 108± 17  7b 126 ± 8  126 ± 29 130 ± 31 145^(‡) ± 19   7c 95 ± 3 115 ± 30108 ± 12 137 ± 46  7d 103 ± 7  106 ± 6  109 ± 8  106 ± 5  10a 121 ± 6 138 ± 3  41^(†) ± 1    9 ± 1^(‡) 10b  26 ± 0.2  0.2^(†) ± 0.3 0^(‡) ± 00* ± 0 10c  93 ± 12  80 ± 13 100 ± 11 99 ± 3 10d  98 ± 13  93 ± 27 91 ±8 96 ± 5 16  132 ± 36 129 ± 10 148 ± 9  161 ± 7^(‡ ) 17  106 ± 3 117^(‡) ± 8   115 ± 11 135 ± 5^(‡ ) 20  94 ± 8 105 ± 3  109 ± 12 116 ±18 21  98 ± 5 127* ± 14  116 ± 9  121 ± 14 ^(a)Effect of lactam andcyclic azahemiacetal derivatives on P_(rhlA)-lacZ expression in E. colitested at 50-200 μg/mL concentrations against 2 μM of C₄-AHL as percentof activity relative to the DMSO treated control. ^(b)*p-value < 0.05,^(†)p-value < 0.02, ^(‡)p-value < 0.01 according to a paired, two-tailedStudent t-test.

Screening Against the Rhl Pathway. To determine the effect of thelactams (7, 16, and 17) and the cyclic azahemiacetal derivatives (10, 20and 21) on the P. aeruginosa rhl AHL mediated pathways, a rhl dependentβ-galactosidase reporter (P_(rhlA)-lacZ) was expressed with rhlR in E.coli (24-25). As expected, and in agreement with published data (24-25),exogenous C₄-AHL activated the rhl β-galactosidase reporter (data notshown). The lactam analogues 7a-d stimulated rhl QS activities at higherconcentrations with moderate potency. Of these, hexylthio lactam 7b wasmost active (Table 2). In contrast, cyclic azahemiacetals with shorteralkylthio chain 10a and 10b inhibited rhl activity, while analogues withlonger alkyl chain 10c and 10d were inactive. The hexylthioazahemiacetal 10b completely inhibited rhl signaling at concentrationsof 100 μg/mL and higher. The strong inhibition observed with propylthio10a and hexylthio 10b azahemiacetal analogues having side chain lengthssimilar to C₄-AHL is in agreement with the structure activityrelationship reported for various synthetic AHL mimetics targeting RhlR(26). The ribolactam analogues 16 and 17 and their cyclic azahemiacetalcounterparts 20 and 21 stimulated rhl activities with moderate potencywith lactams being more effective (e.g., 16 vs. 20).

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What is claimed:
 1. A compound having a structure of formula (I):

wherein R¹ is OH and R² is H, or R¹ and R² taken together are oxo; R³ isselected from the group consisting of C₇-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H,C₁-C₂₀alkyleneCO₂—C₁-C₃alkyl, C₁-C₂₀alkyleneCO₂—C₅-C₆alkyl,C₁-C₄alkyleneCO₂—C₁-C₆alkyl, C₆-C₂₀alkyleneCO₂—C₁-C₆alkyl, andC₁-C₂₀alkylene-amino, and the alkyl or alkylene group of R³ does notcomprise a carbon-carbon double bond and is not further substituted; R⁴and R⁵ are each independently H or OH, or R⁴ and R⁵ taken together withthe carbons that they are attached form a 4-7 membered cyclic orheterocyclic ring, and the ring is not further substituted; X is NR⁶;and R⁶ is H; or a salt or ester thereof.
 2. A compound having astructure of formula (I):

wherein: R¹ and R² are each independently H or OH, or R¹ and R² takentogether are oxo; R³ is selected from the group consisting ofC₇-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H, C₁-C₂₀alkyleneCO₂—C₁-C₃alkyl,C₁-C₂₀alkyleneCO₂—C₅-C₆alkyl, C₁-C₄alkyleneCO₂—C₁-C₆alkyl,C₆-C₂₀alkyleneCO₂—C₁-C₆alkyl, and C₁-C₂₀alkylene-amino, and the alkyl oralkylene group of R³ does not comprise a carbon-carbon double bond andis not further substituted; both R⁴ and R⁵ are OH; X is NR⁶; and R⁶ isH; or a salt or ester thereof.
 3. The compound of claim 1, wherein bothR⁴ and R⁵ are H.
 4. The compound of claim 1, wherein R³ is C₇-C₂₀alkyl.5. The compound of claim 1, wherein R³ is selected from the groupconsisting of C₁-C₂₀alkyleneCO₂H, C₁-C₂₀alkyleneCO₂—C₁-C₃alkyl,C₁-C₂₀alkyleneCO₂—C₅-C₆alkyl, C₁-C₄alkyleneCO₂—C₁-C₆alkyl,C₆-C₂₀alkyleneCO₂—C₁-C₆alkyl and C₁-C₂₀alkylene-amino.
 6. A method ofinhibiting bacterial quorum sensing or inhibiting formation of a biofilmcomprising contacting bacteria with the compound of claim
 1. 7. Themethod of claim 6, wherein the bacteria is selected from the groupconsisting of: Acinetobacter baumannii, Aeromonas hydrophila, Aeromonassalmonicida, Agrobacterium tumefaciens, Brucella melitensis,Burkholderia cenocepacia, Burkholderia mallei, Burkholderiapseudomallei, Burkholderia vietnamiensis, Chromobacterium violaceum,Enterobacter agglomeran, Erwinia carotovora, Erwinia chrysanthemi,Escherichia coli, Nitrosomas europaea, Obesumbacterium proteus, Pantoeaagglomerans, Pantoea stewartii, Pseudomonas aureofaciens, Pseudomonasaeruginosa, Pseudomonas fluorescens, Pseudomonas fuscovaginae,Pseudomonas syringae, Ralstonia solanacearum, Rhizobium etli, Rhizobiumleguminosarum, Rhodobacter sphaeroides, Serratia liquefaciens, Serratiamarcescens, Vibrio anguillarum, Vibrio fischeri, Vibrioparahaemolyticus, Vibrio salmonicida, Xanthomonas campestris,Xenorhabdus nematophilus, Yersinia enterocolitica, Yersinia pestis,Yersinia pseudotuberculosis, Yersinia medievalis, Yersinia ruckeri, andcombinations thereof.
 8. The method of claim 6, wherein the contactingcomprises administering the compound or the composition to a subjectsuffering from a bacterial infection.
 9. The method of claim 8, furthercomprising administering a second agent to the subject.
 10. The methodof claim 9, wherein the second agent is an antibiotic selected from thegroup consisting of a penicillin, a selexid, a cephalosporin, atetracycline, a rifamycin, gentamycin, clindamycin, a fluoroquinolone, amonobactamer, a carbapeneme, a macrolide, a polymyxin, anaminoglycoside, tobramycin, a sulfonamide, a fusidine, a vancomycin, anoxazolidinone, a metronidazole, a corticosteroid, hydrocortisone,triamcinolone, betamethasone, and combinations thereof.
 11. A method oftreating a subject suffering from an infection comprising administeringto the subject an effective amount of the compound of claim
 1. 12. Themethod of claim 11, further comprising administering to the subject asecond therapeutic, wherein the second therapeutic is an antibiotic. 13.The method of claim 12, wherein the antibiotic is selected from apenicillin, a selexid, a cephalosporin, a tetracycline, a rifamycin,gentamycin, clindamycin, a fluoroquinolone, a monobactamer, acarbapeneme, a macrolide, a polymyxin, an aminoglycoside, tobramycin, asulfonamide, a fusidine, a vancomycin, an oxazolidinone, ametronidazole, a corticosteroid, hydrocortisone, triamcinolone,betamethasone, and combinations thereof.
 14. The method of claim 11,wherein the infection is a P. aeruginosa infection.
 15. A compoundhaving a structure of formula (II):

wherein R¹ and R² are each independently H or OH, or R¹ and R² takentogether are oxo; R³ is selected from the group consisting ofC₃-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H, C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl andC₁-C₂₀alkylene-amino, and the alkyl or alkylene group of R³ does notcomprise a carbon-carbon double bond and is not further substituted; R⁴and R⁵ are each independently H or OH, wherein at least one of R⁴ and R⁵is OH; X is NR⁶; and R⁶ is H; or a salt or ester thereof.
 16. A compoundhaving a structure of formula (III):

wherein R¹ and R² are each independently H or OH, wherein at least oneof R¹ and R² is OH or R¹ and R² taken together are oxo; R³ is selectedfrom the group consisting of C₃-C₂₀alkyl, C₁-C₂₀alkyleneCO₂H,C₁-C₂₀alkyleneCO₂—C₁-C₆alkyl and C₁-C₂₀alkylene-amino, and the alkyl oralkylene group of R³ does not comprise a carbon-carbon double bond andis not further substituted; R⁴ and R⁵ are each independently H or OH, orR⁴ and R⁵ taken together with the carbons that they are attached form a4-7 membered cyclic or heterocyclic ring, and the ring is not furthersubstituted; X is NR⁶; and R⁶ is C(O)alkyl, and the alkyl group of R⁶ isnot further substituted; or a salt or ester thereof.
 17. A method ofinhibiting bacterial quorum sensing or inhibiting formation of a biofilmcomprising contacting bacteria with the compound of claim
 15. 18. Amethod of inhibiting bacterial quorum sensing or inhibiting formation ofa biofilm comprising contacting bacteria with the compound of claim 16.19. A method of treating a subject suffering from an infectioncomprising administering to the subject an effective amount of thecompound of claim
 15. 20. A method of treating a subject suffering froman infection comprising administering to the subject an effective amountof the compound of claim
 16. 21. A method of inhibiting bacterial quorumsensing or inhibiting formation of a biofilm comprising contactingbacteria with the compound of claim
 2. 22. A method of treating asubject suffering from an infection comprising administering to thesubject an effective amount of the compound of claim 2.